315. A and B can do a work in 8 days, 13, and C can do the same work in 12 days. A, B and C together can finish it in 6 days. A and C together will do it in_________?

A. 4 days
B. 6 days
C. 8 days
D. 12 days
✅ The correct answer is option C. 8 days.
(A + B + C)’s 1 day’s work = 1/6; (A + B)’s 1 day’s work = 1/8 (B + C)’s 1 day’s work = 1/12 (A + C)’s 1 day’s work = ( 2 X 1/6 ) – ( 1/8 + 1/12 ) = ( 1/3 – 5/24 ) = 3/24 = 1/8 So, A and C together will do the woirk in 8 days.

319. A bag contains 1 rupee, 2 rupee and 5 rupee coins amounting to Rs.264. If the ratio of the number of these coins is 3:5:4, find the number of 1 rupee coins.

A. 66
B. 48
C. 24
D. 8
✅ The correct answer is option C. 24.
Let the number of 1 rupee, 2 rupee and 5 rupee coins be 3x, 5x and 4x. (1*3x)+(2*5x)+(5*4x)=264 3x+10x+20x=264 33x=264 x=8 No. of 1 rupee coins

= 3x = 24