Question

5 men and 12 boys finish a piece of work in 4 days, 7 men and 6 boys do it in 5
days. The ratio between the efficiencies of a man and boy is?
A. 1:2
B. 2:1
C. 2:3
D. 6:5

Answer 1

Solve at yourself thus is same question in ex. 3.6 Q-2 (ii)

Answer 2

Answer:

Option D  6:5

Step-by-step explanation:

Let one man's one day work be x and one boy's one day work be y, therefore

5x+12y = 1/4 and 7x+6y =1/5

Now, solving the above for  the values of x and y....

5x+12y = 1/4.....multiplying this equation by 7 to eliminate x

7x+6y = 1/5....multiplying this equation by 5 to eliminate x

We get..

35x+84y=7/4...equation 1

35x+30y=1.....equation 2

Subtracting eg 1 and 2 we get

54y =7/4-1

54y = 3/4

y =3/4*54

y=1/72

Now putting the value of y in equation 5x+12y=1/4, we get

5x+12*1/72=1/4

5x=1/4-1/6

5x=1/12

x=1/60

Therefore x/y= 1/60/1/72

x/y = 72/60

x/y=6/5

Therefore the ratio of efficiencies of man :boy is 6:5