sandy wrote:

A certain machine drills 30 holes in 8 minutes. At that constant rate, how many holes will 4 such machines drill in 1\frac{1}{3} hours?

(A) 300

(B) 900

(C) 960

(D) 1,200

(E) 2,560

Here

1\frac{1}{3} = 80minutes

Therefore we KNow-

Amount of work = Rate * Time

Amount of work = 30 holes

Rate = we need to find it

Time = 8 minutes

No. of machine = 1

so in first case

30 = 1 * R * 8

or Rate=

\frac{30}{8}Now for the 2nd case

Amount of work = We need to find out

Rate =

\frac{30}{8}No. of machine = 4

Time = 80 minutes

Therefore

A =R * T

A = 4 *

\frac{30}{8} * 80

or A = 1200 holes

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