Question

Six machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the job in 8 days?A. 2

B. 3
C. 4
D. 6
E. 8

Answer 1

B

Explanation:

6 machines complete the job in 12 days;

the more machine you have faster the job will be done, inverse proportion

6 machines --- 12 days

x machines -- 8 days

you reduce the number of days by a factor of 1.5 (12/1.5)

sou you hvae to increase the number of machines by 1.5

6 x 1.5 = 9, so you will need 3 additional machines