three man A, B and C working together can do a job in 6 hours less time than A alone , in 1 hour less time than B alone and in one half time needed by C when working alone .then A and B together can do the job in ; A.3/4 hour B.5/4 hour C.4/3 hour D.1/4 hour
Answers
Answer:
job in 6 hours less time than A alone, in 1 hour less
time than B alone and in one half the time needed by C when working alone. Then A and B together
can do the job in
A) \( \Large \frac{2}{3} \)hour
B) \( \Large \frac{2}{3} \)hour
C) \( \Large \frac{3}{2} \)hour
D) \( \Large \frac{4}{3} \)hour
Correct Answer:
D) \( \Large \frac{4}{3} \)hour
Description for Correct answer:
Let x is total time taken by \( \Large \left(A + B + C\right) \)
\( \Large \left(A + B\right) 's \) efficiency
= \( \Large 2 - 1 = 1 \)
\( \Large 2x=\sqrt{ \left(6-x\right) \left(1-x\right) }=3x^{2}+7x-6=0 \)
x=\( \Large \frac{2}{3} \)
A alone does=\( \Large \frac{2}{3}+6=\frac{20}{3} \)
hours, B alone \( \Large \frac{2}{3}+1=\frac{5}{3} \) hrs
\( \Large A+B \) can do it in
=\( \Large \frac{4}{3} \) hours
the answer will be 4/3.
