Question

A and 13 together can do a piece of work in 12 days: B and C can do it in 20 days whilci C and A can do it in 15 days. A. B and C all working together can do it In

(a) 6 days

(b) 9 days

(c) 10 days

(d) $10\frac{1}{2}$ days

Answer 1

A and B's 1 day's work $=\frac{1}{12}$

B and C's 1 day's work $=\frac{1}{20}$

C and A's 1 day's work $=\frac{1}{15}$

Adding we get,

2(A,B and C)'s 1 day's work

$=\frac{1}{12}+\frac{1}{20}+\frac{1}{15}$

$=\frac{5+3+4}{60}=\frac{12}{60}=\frac{1}{5}$

$\therefore$ A,B and C's 1 days work

$=\frac{1}{5}\times \frac{1}{2}=\frac{1}{10}$

$\therefore$ That will finish the work in =10 days