NCERT Class 7 Ganit Prakash 1 Chapter 01 Large Numbers Around Us PDF Download

Chapter 1: Large Numbers Around Us

1.1 A Lakh Varieties!

Eshwarappa is a farmer in Chintamani, a town in Karnataka. He visits the market regularly to buy seeds for his rice field. During one such visit he overheard a conversation between Ramanna and Lakshmamma. Ramanna said, "Earlier our country had about a lakh varieties of rice. Farmers used to preserve different varieties of seeds and use them to grow rice. Now, we only have a handful of varieties. Also, farmers have to come to the market to buy seeds".

Lakshmamma said, "There is a seed bank near my house. So far, they have collected about a hundred indigenous varieties of rice seeds from different places. You can also buy seeds from there."

You may have heard the word 'lakh' before. Do you know how big one lakh is? Let us find out.

Eshwarappa shared this incident with his daughter Roxie and son Estu.

Estu was surprised to know that there were about one lakh varieties of rice in this country. He wondered "One lakh! So far I have only tasted 3 varieties. If we tried a new variety each day, would we even come close to tasting all the varieties in a lifetime of 100 years?"

What do you think? Guess.

But how much is one lakh? Observe the pattern and fill in the boxes given below.

The largest 3-digit number is 999

The smallest 4-digit number is _____

The largest 4-digit number is _____

The smallest 5-digit number is _____

The largest 5-digit number is _____

The smallest 6-digit number is 1,00,000

\( 1,00,000 \) is read as "One Lakh"

Roxie and Estu found that if they ate one variety of rice a day, they would come nowhere close to a lakh in a lifetime! Roxie suggests, "What if we ate 2 varieties of rice every day? Would we then be able to eat 1 lakh varieties of rice in 100 years?"

What if a person ate 3 varieties of rice every day? Will they be able to taste all the lakh varieties in a 100 year lifetime? Find out.

Estu said, "We know how many days there are in a year - 365, if we ignore leap years. If we live for \( y \) years, the number of days in our lifetime will be \( 365 \times y \)."

Teacher's Note

When you see a problem asking "how many days in \( y \) years," remember to multiply 365 by the number of years. If the problem says "100 years," then \( y = 100 \) and you calculate \( 365 \times 100 \). Always check whether the result makes sense by comparing it to one lakh (100,000).

Choose a number for \( y \). How close to one lakh is the number of days in \( y \) years, for the \( y \) of your choice?

Figure it Out

1. According to the 2011 Census, the population of the town of Chintamani was about 75,000. How much less than one lakh is 75,000?
2. The estimated population of Chintamani in the year 2024 is 1,06,000. How much more than one lakh is 1,06,000?
3. By how much did the population of Chintamani increase from 2011 to 2024?

Getting a Feel of Large Numbers

You may have come across interesting facts like these:

• The world's tallest statue is the 'Statue of Unity' in Gujarat depicting Sardar Vallabhbhai Patel. Its height is about 180 metres.
• Kunchikal waterfall in Karnataka is said to drop from a height of about 450 metres.

It is not always easy to get a sense of how big these measurements are. But, we can get a better sense of their size when we compare them with something familiar. Let us see an example.

Look at the picture on the right. Somu is 1 metre tall. If each floor is about four times his height, what is the approximate height of the building?

Which is taller - The Statue of Unity or this building? How much taller? __________ m.

We can see that the height of the Statue of Unity is close to 4 times the height of Somu's building.

Teacher's Note

When you are given a comparison problem like this, always identify what you are comparing. Here you compare the Statue of Unity (180 m) with the building's height. If the building is 4 floors high and each floor is 4 metres, the building is 16 metres. Then the difference is \( 180 - 16 = 164 \) metres. Write down these steps clearly so you don't lose marks.

How much taller is the Kunchikal waterfall than Somu's building? __________ m.

How many floors should Somu's building have to be as high as the waterfall? __________ .

Key Points

• One lakh is written as 1,00,000 and is the smallest 6-digit number. It lies between the largest 5-digit number (99,999) and comes right after it.
• To find the number of days in several years, multiply the number of years by 365 (ignoring leap years). For example, 100 years equals \( 365 \times 100 = 36,500 \) days.
• When comparing very large measurements, use familiar objects as reference points. For instance, if you know Somu's height is 1 metre, you can use that to estimate the height of buildings or monuments.
• Differences between numbers can be found by subtraction. To find how much more or less one number is than another, subtract them in the correct order.

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