lcm and hcf Model Questions & Answers, Practice Test for ibps rrb po officer scale 1 prelims 2024

Answer: (c)

The LCM of 6, 7, 8 , 9 and 10 = 2520

The greatest number of 6 digits = 999999

Dividing 999999 by 2520, we get 2079 as remainder.

Hence, the 6-digit number divisible by 2520, is (999999 – 2079), or 997920.

Since 6 – 4 = 2, 7 – 5 = 2, 8 – 6 = 2, 9– 7 = 2, 10 – 8 = 2, the remainder in each case is less than the divisor by 2.

∴ the required number = 997920 – 2 = 997918

Answer: (a)

Let two numbers by 29x and 29y.

∴ 29x + 29y = 232⇒x + y = 8

⇒(x, y) = (1,7), (3,5)

Since, one such pair is 87 and 145.

Hence, the other pairs is 203 and 29.

Answer: (b)

Let P = 10, q = 11, r = 13 (Co-prime numbers)

LCM of (10, 11, 13) = 1430

HCF (10, 11, 13) = 1

mn = 1430 × 1 = 1430

Also, pqr = 10 × 11 × 13 = 1430

So, mn = pqr

Answer: (c)

2.$\ov6$ - 1.$\ov9$ = 2$6/9 - 2 = (2 -2) + 6/9 = 6/9$ = 0.$\ov6$

Answer: (b)

Value of 0.$\ov9$ = $9/9$ = 1

Value of 0.9 = $9/{10}$

difference = 1 - $9/{10} = 1/{10}$ = 0.1