Question

A room has to be painted and worker A does 1/3 of the work then leaves. Next worker B does 1/4 of the remaining work and then leaves and finally worker C does 1/5 of the remaining work and then leaves.
What fraction of the room still needs to be painted?
a)3/5
b)2/5
c)13/60
d)7/15

Answer 1

The answer is c) 13/60.

Explanation: the answer is 13/60. This is because in order to find the sum of the fractions you have to add them. In order to add fractions they have to have common denominators. The least common multiple of 3, 4, and 5 is 60 so your denominator is 60 now you have to multiply the numerator by whatever you multiplied the denominator by to get 60. For 1/3 the new fraction would be 20/60 for 1/4 the new fraction would be 15/60 and for 1/5 the new fraction would be 12/60. When you add these fractions together you get 47/60. Now you have to do 60/60 - 47/60 and you get 13/60. Because this is in simplest form the answer is 13/60

Answer 2

Answer:

2/5, or B.

Explanation:

Let's make the total work needed x. Then Worker A does 1/3x and 2/3x work is left for the other workers to do (we know this because 1-1/3 = 2/3). Thus, worker B comes and does 1/4 of the remaining work, which is 2/3x. So, worker B does 1/4*(2/3x), which gives you 1/6x. Then, to find the work left over for worker C, we subtract 1/6x from 2/3x, which gives us 3/6x, or 1/2x. Then. worker C does 1/5 of 1/2x, giving us 1/5*(1/2x), which is 1/10x. To find the remaining work, we do 1/2x - 1/10x to get 4/10x, which simplifies to 2/5x. Therefore, the answer is 2/5, or B.