Get easy Class 7 Maths Chapter 1 Exercise 1.2 solutions with step-by-step answers for the +1000 and +10 button questions, including one lakh and number-of-presses problems.
Class 7 Maths Chapter 1 Exercise 1.2 Solutions
Students looking for Class 7 Maths Chapter 1 Exercise 1.2 Solutions can use this page to understand the questions based on the +1000 and +10 buttons.
These questions are designed to strengthen the idea of place value and help students understand how many thousands or tens are needed to make a particular number.
The key idea is very simple:
- One press of the +1000 button adds 1,000.
- One press of the +10 button adds 10.
So, instead of doing complicated calculations, we can divide the required number by the value added by one button press.
Question Information
| Information | Details |
|---|---|
| Class | 7 |
| Subject | Mathematics |
| Book | Ganita Prakash |
| Chapter | 1 – Large Numbers Around Us |
| Exercise | 1.2 |
| Questions | 1 and 2 |
| Main Concept | Place value, thousands and tens |
| Difficulty | Easy |
Question 1 — The Thoughtful Thousands
The Thoughtful Thousands has only a +1000 button.
How many times should the button be pressed to show the following numbers?
Key Idea
Every press adds:
1,0001,000
Therefore:
Number of presses=Required number1,000\text{Number of presses}=\frac{\text{Required number}}{1,000}
We can use this idea for every part.
(a) Three thousand
We need to make:
3,0003,000
Each press adds:
1,0001,000
Therefore:
3,000÷1,000=33,000\div1,000=3
Final Answer
The button should be pressed 3 times.
(b) 10,000
We need:
10,00010,000
Therefore:
10,000÷1,000=1010,000\div1,000=10
Final Answer
The button should be pressed 10 times.
(c) 53,000
We need:
53,00053,000
Therefore:
53,000÷1,000=5353,000\div1,000=53
Final Answer
The button should be pressed 53 times.
(d) 90,000
We need:
90,00090,000
Therefore:
90,000÷1,000=9090,000\div1,000=90
Final Answer
The button should be pressed 90 times.
(e) One lakh
We know:
1 lakh=1,00,0001\text{ lakh}=1,00,000
Therefore:
1,00,000÷1,000=1001,00,000\div1,000=100
Final Answer
The button should be pressed 100 times.
Why?
One press gives 1 thousand.
So 100 presses give:
100×1,000=1,00,000100\times1,000=1,00,000
which is one lakh.
(f) 153 times
The question gives the number of presses as:
153153
Each press adds 1,000.
Therefore:
153×1,000=1,53,000153\times1,000=1,53,000
Final Answer
153 presses show 1,53,000.
(g) How many thousands are required to make one lakh?
We know:
1 lakh=1,00,0001\text{ lakh}=1,00,000
and:
1 thousand=1,0001\text{ thousand}=1,000
Therefore:
1,00,000÷1,000=1001,00,000\div1,000=100
Final Answer
100 thousands\boxed{100\text{ thousands}}
are required to make one lakh.
Quick Table — Question 1
| Required number / Presses | Answer |
|---|---|
| 3,000 | 3 presses |
| 10,000 | 10 presses |
| 53,000 | 53 presses |
| 90,000 | 90 presses |
| 1 lakh | 100 presses |
| 153 presses | 1,53,000 |
| 1 lakh | 100 thousands |
Why Does the +1000 Button Work This Way?
The button adds exactly:
1,0001,000
every time.
For example:
1 press=1,0001\text{ press}=1,000 2 presses=2,0002\text{ presses}=2,000 3 presses=3,0003\text{ presses}=3,000
and so on.
Therefore:
n presses=n×1,000n\text{ presses}=n\times1,000
This is simply repeated addition.
Common Mistake in Question 1
Do not confuse 1,000 with 10,000 or 1,00,000.
Remember:
1 thousand=1,0001\text{ thousand}=1,000 10 thousand=10,00010\text{ thousand}=10,000 100 thousand=1,00,000=1 lakh100\text{ thousand}=1,00,000=1\text{ lakh}
Question 2 — The Tedious Tens
The Tedious Tens has only a +10 button.
How many times should it be pressed to show the given numbers?
Key Idea
Each press adds:
1010
Therefore:
Number of presses=Required number10\text{Number of presses}=\frac{\text{Required number}}{10}
Let’s solve each part.
(a) Five hundred
We need:
500500
Therefore:
500÷10=50500\div10=50
Final Answer
The button should be pressed 50 times.
Check:
50×10=50050\times10=500
(b) 780
We need:
780780
Therefore:
780÷10=78780\div10=78
Final Answer
The button should be pressed 78 times.
Check:
78×10=78078\times10=780
(c) 1,000
We need:
1,0001,000
Therefore:
1,000÷10=1001,000\div10=100
Final Answer
The button should be pressed 100 times.
(d) 3,700
We need:
3,7003,700
Therefore:
3,700÷10=3703,700\div10=370
Final Answer
The button should be pressed 370 times.
(e) 90,000
We need:
90,00090,000
Therefore:
90,000÷10=9,00090,000\div10=9,000
Final Answer
The button should be pressed 9,000 times.
(f) One lakh
We know:
1 lakh=1,00,0001\text{ lakh}=1,00,000
Therefore:
1,00,000÷10=10,0001,00,000\div10=10,000
Final Answer
The button should be pressed 10,000 times.
Check:
10,000×10=1,00,00010,000\times10=1,00,000
(g) 435 times
The question gives:
435 presses435\text{ presses}
Each press adds 10.
Therefore:
435×10=4,350435\times10=4,350
Final Answer
435 presses show 4,350.
Quick Table — Question 2
| Required number / Presses | Answer |
|---|---|
| 500 | 50 presses |
| 780 | 78 presses |
| 1,000 | 100 presses |
| 3,700 | 370 presses |
| 90,000 | 9,000 presses |
| 1 lakh | 10,000 presses |
| 435 presses | 4,350 |
Why Does the +10 Button Work This Way?
Every press adds 10.
So:
1 press=101\text{ press}=10 2 presses=202\text{ presses}=20 10 presses=10010\text{ presses}=100 100 presses=1,000100\text{ presses}=1,000 1,000 presses=10,0001,000\text{ presses}=10,000
Therefore:
n presses=n×10n\text{ presses}=n\times10
If we know the target number and want to find the number of presses, we divide by 10.
Comparing the Two Buttons
The two questions show an important place-value relationship.
| Button | Value added in one press |
|---|---|
| +1000 | 1,000 |
| +10 | 10 |
One press of the +1000 button adds:
1,000÷10=1001,000\div10=100
times as much as one press of the +10 button.
For example:
100×10=1,000100\times10=1,000
So 100 presses of +10 have the same numerical effect as 1 press of +1000.
This is a useful way to connect the question with place value.
A Simple Rule to Remember
For the +1000 button
To find the number of presses:
Target number÷1,000\boxed{\text{Target number}\div1,000}
To find the number displayed after a given number of presses:
Presses×1,000\boxed{\text{Presses}\times1,000}
For the +10 button
To find the number of presses:
Target number÷10\boxed{\text{Target number}\div10}
To find the number displayed after a given number of presses:
Presses×10\boxed{\text{Presses}\times10}
Why This Method Is Easy
There is no need for a complicated formula.
The button tells us exactly how much is added each time.
If the button adds 1,000, divide by 1,000 to find how many presses are needed.
If the button adds 10, divide by 10.
For the reverse question, simply multiply the number of presses by the amount added in each press.
Common Mistakes
Mistake 1: Dividing by the wrong number
For the +1000 button, divide by 1,000, not 100.
For the +10 button, divide by 10.
Mistake 2: Losing zeroes
For example:
1,00,000÷10=10,0001,00,000\div10=10,000
not 1,000.
Mistake 3: Confusing multiplication and division
- Target number → number of presses: divide
- Number of presses → displayed number: multiply
Key Concept for Revision
The entire exercise can be understood through two relationships:
Number shown=Number of presses×Value of one press\boxed{\text{Number shown}=\text{Number of presses}\times\text{Value of one press}}
and
Number of presses=Number shownValue of one press\boxed{\text{Number of presses}=\frac{\text{Number shown}}{\text{Value of one press}}}
These relationships help students solve similar questions quickly.
More Class 7 Maths Chapter 1 Resources
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- [Internal link: Class 7 Maths Chapter 1 MCQs]
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- [Internal link: Class 7 Maths Chapter 1 Practice Test]
- [Internal link: Class 7 Maths Chapter-wise Solutions]
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PART B — PRACTICE QUESTIONS
Practice Question 1
A number machine has only a +500 button. How many times should the button be pressed to show:
- 2,500
- 8,000
- 25,000
- 1,00,000
Solution
Each press adds:
500500
1. For 2,500
2,500÷500=52,500\div500=5
So, 5 presses are needed.
2. For 8,000
8,000÷500=168,000\div500=16
So, 16 presses are needed.
3. For 25,000
25,000÷500=5025,000\div500=50
So, 50 presses are needed.
4. For 1,00,000
1,00,000÷500=2001,00,000\div500=200
So, 200 presses are needed.
Final Answers
5, 16, 50, 200\boxed{5,\;16,\;50,\;200}
presses respectively.
Explanation
We divide each target number by 500 because every press increases the displayed number by 500.
Practice Question 2
A number machine has only a +25 button.
- How many presses are needed to show 500?
- How many presses are needed to show 2,000?
- What number will appear after 125 presses?
Solution
Each press adds:
2525
1. To show 500
500÷25=20500\div25=20
Therefore, 20 presses are needed.
2. To show 2,000
2,000÷25=802,000\div25=80
Therefore, 80 presses are needed.
3. After 125 presses
Now we multiply:
125×25125\times25 =125×(100÷4)=125\times(100\div4) =3,125=3,125
Therefore, the number displayed is:
3,125\boxed{3,125}
Final Answers
- 20 presses
- 80 presses
- 3,125
Explanation
When the target number is known, divide by the amount added in one press. When the number of presses is known, multiply by the amount added each time.
PART C — REMEMBER
- One press of +1000 adds 1,000.
- One press of +10 adds 10.
- To find presses from a target number, divide by the value of one press.
- To find the displayed number from the number of presses, multiply.
- One lakh is:1,00,0001,00,000so it contains 100 thousands.
One-line trick
Target → Divide. Presses → Multiply.
Internal Links
- Class 7 Maths Chapter 1 Solutions
- Class 7 Maths Chapter 1 Notes
- Class 7 Maths Chapter 1 Important Questions
- Class 7 Maths Chapter 1 MCQs
- Class 7 Maths Chapter 1 Practice Questions
- Class 7 Maths Chapter 1 Practice Test
- Class 7 Maths Chapter-wise Solutions