CSAT 2021

Q. Integers are listed from 700 to 1000. In how many integers is the sum of the digits 10?

(a) 6
(b) 7
(c) 8
(d) 9
Correct Answer: (d) 9

Question from UPSC Prelims 2021 CSAT Paper

Explanation :

Integers are listed from 700 to 1000

The sum of the digits of an integer is 10 if the digits add up to 10. For example, the number 703 has a digit sum of 7 + 0 + 3 = 10. We can find all integers between 700 and 1000 that have a digit sum of 10 by listing them out:

703, 712, 721, 730, 802, 811, 820, 901, 910.

There are 9 integers between 700 and 1000 that have a digit sum of 10. So the correct answer is (d) 9.

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