IBPS RRB PO Prelims 12 sep 2020 Questions and Answers Detailed Explanation

Answer: (d)

Let the total capacity = 72 units (LCM of 24, 36 and 18)

Efficiency of A =  $72/24$ = 3

Efficiency of B =  $72/36$ = 2

Efficiency of C = –$72/18$ = –4

Number of units filled in 3 minutes = 3 + 2 – 4 = 1

So, 72 – 5 = 67 unit will be filled in 67 × 3 = 201 minutes

Remaining 5 units will be filled in the next 2 minutes

Hence, the total time = 201 + 2 = 203 minutes.

Answer: (d)

? = √{784} × 7 + 352 × 25% = 28 × 7 + 88 = 196 + 88 = 284 Hence, the answer is D.

Answer: (b)

? = 15.33² – 12.94² + 22.06² – 35.65

= 15² – 13² + 22² – 35

= 225 – 169 + 484 – 35

= 505.

Hence, the answer is B.

Answer: (d)

Let the age of A be x years

Six years ago

A’s age = x – 6

A’ s uncle’s age = 6x – 36

Two years hence

A’s age = x + 2

A’s uncle ‘s age = 3x+6

A’ s uncle’s age six years ago + 8 = A’s uncle ‘s age two years hence

6x – 36 + 8 = 3x + 6

6x – 28 = 3x + 6

x = 11.33 years

Hence, the answer is D.

Answer: (a)

Let speed of stream = x km/hr

Speed of boat = 4x km/hr

$45/\text"4x - x" - 45/\text"4x + x" = 2$

$45/3x - 45/5x = 2$

$1/x$(15 - 9) = 2

x = $6/2$ = 3

Hence, the speed of stream = x = 3 km/hr.

Answer: (c)

Let the total work = 18 units (LCM of 6 and 9)

Efciency of A and B together = $18/6$ = 3

Efciency of A alone = $18/9$ = 2

Efciency of B alone = Efciency of A and B together – Efciency of A alone

= 3 – 2 = 1

Hence, the required number of days = $3/8 x 18$ = $27/4$