Number System 1

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1. find the differences in the place-values of two fives in the numeral 653852.

Solution: Place-value of 5 at ten thousands place = 50000

Place-value of 5 at tens place = 50

Required difference = 50000 - 50 = 49950

2. How many four-digit numbers are there?

Solution: Largest 4-digit number = 1000

Smallest 4-digit number = 1000

Number of all 4-digit numbers = (9999 - 1000) + 1 = 8999 + 1 = 9000

3. Write all 3-digit numbers formed by using the digits 2,5 and 7taking each digit only once in each number.

Solution: Keeping 2 at unit place, numbers formed are 752 and 572

Keeping 5 at the unit place, numbers formed are 275 and 725

Keeping 7 at unit place, numbers formed are 257 and 527

So, the required numbers are 257,275,527,572,725 and 752.

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