4 boys or 7 girls can complete a piece of work in 18 days. How many days will 12 boys and 21 girls together take to complete this job?
Answer & explanation
Correct answer: option 1
4 Boys = 7 Girls
Boys : Girls = 7 : 4 (Efficiency)
Total work = 4(7) x 18 days = 504 units,
⇒ Time required by 12 Boys and 21 Girls to complete total work = \(\frac{504}{12(7) + 21(4)}\) = \(\frac{504}{168}\) = 3 days, ..(\(\frac{Work}{Efficiency}\) = Time )