Information and Communication Technology - Number System
21. If 5432*7 is divisible by 9, then the digit in place of * is
- Option : B
- Explanation : A number is divisible by 9 if the sum of its digits is divisible by 9.Let the number be x. ∴5 + 4 + 3 +2 + x + 7 = 21 + x If we put x = 6, then it is divisible by 9. ∴ x= 6 Hence, the digit in place of * is 6.
- Option : A
- Explanation : Here, 280 is a multiple of 35. ∴ Required remainder = Remainder obtained on dividing 115 by 35 = 10
23. Sum and difference of two numbers are 25 and 15 respectively. The greater number is
- Option : C
- Explanation : Let two numbers are x and y respectively. Now, according to the question, x + y = 25 ... (i) and x - y = 15 ... {ii) Solving Eqs(i) and (ii), we get x=20 and y=5 ∴ Greater number = x = 20
24. The digit in unit's place of the product 81 x 82 x 83 x ... x 89 is
- Option : A
- Explanation : The digit in unit's place = Unit's digit in the product 1 x 2 x 3 x ... x 9 =0
25. Find the unit digit in the product of (268 x 539 x 826 x 102).
- Option : C
- Explanation : Unit digit in 268 x 539 x 826 x 102 = Unit digit in 8 x 9 x 6 x 2 = Unit digit in 72 x 12 = Unit digit in 2 x 2 = 4
