Question

7. A and B can do a piece of work in 72 days: B and C can do it in 120 days: A and C can do it in 90 days. In what time can A, B and C together finished the work? ​

Answer 1

Answer:

60 days

According to question,

(A + B)’s one day’s work = \frac{1}{72}

(B + C)’s one day’s work = \frac{1}{120}

and (C + A)’s one day’s work = \frac{1}{90}

On adding all three,

2 (A + B + C)’s one day’s work = \frac{1}{72}+ \frac{1}{120}+ \frac{1}{90}

= \frac{5+3+4}{360} = \frac{1}{30}

∴ (A + B + C)’s one day’s work = \frac{1}{60}

∴ A, B and C together can finish the whole work in 60 days.

hence proved that A,B,C together finish work in 60 days

Answer 2

60 days is ans

Step-by-step explanation:

(A+B) one days work = 1/72

(B+C) one days work =1/120

and

(C+A) one days work = 1/90

on adding all three ,

2 (A+B+C) one days work = 1/72 +1/120 + 1/90

=5+3+4/360= 1/60

so A B and C together finish the work in 60 days