NCERT Solutions for Class 7th Maths Chapter 3 Summary — In-text Question

Book page 65 Updated on2026-09-19

Q1.
The largest prime found so far has 4,10,24,320 digits! It was discovered on October 12, 2024. If I start writing this number, how long could it take me?
Answer

Writing it out by hand would take you well over a year of non-stop work.

Number of digits = 4,10,24,320 = 41,024,320
Suppose you write one digit every second, without ever stopping
Seconds needed = 41,024,320
Minutes = 41,024,320 ÷ 60 ≈ 6,83,739
Hours = 6,83,739 ÷ 60 ≈ 11,396
Days = 11,396 ÷ 24 ≈ 475 days — about 1 year and 4 months

And nobody writes for 24 hours a day. Writing for 8 hours every single day:

11,396 hours ÷ 8 hours a day ≈ 1,425 days ≈ about 4 years

Filling ordinary notebook pages at roughly 2,000 digits a page, the number would run to more than 20,000 pages.

Did you know? The number is 2136279841 − 1. Primes of the form 2n − 1 are called Mersenne primes, and they are how nearly every record-breaking prime has been found. No one writes such numbers out — they are stored and checked by computers.
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