NIELIT 2017

Question

aamir and birju can cut 5000 g of wood in 20 min.birju and charles can cut 5000 g of wood in 40 min.charles and aamir can cut 5 kg of wood in 30 min.how much time charles will take to cut 5 kg wood alone??

Answer 1

I think i should be 240 min

let CA capacity of Amir, CB capacity of Birju, CC capacity of Charles.

now Capacity=Work/Time

then form the question we can write

CA+CB=5000/20=500/2   => 2CA+2CB=500...............1

CB+CC=5000/40=250/2   => 2CB+2CC=250.................2

CC+CA=5000/30=500/3   => 3CC+3CA=500.................3

Now Solving the equation 1,2,3 for CC(As we need to answer about charles) we get CC=125 / 6

Again CC=work to be done by charles/Time take to do the work (t)

125/6=5000/t

t  =  (5000*6)/125

    = 240 Min

hope it helps

Answer 2

Let capacity of each person to cut 5000 g of wood be,

AAMIR-  A;

BIRJU - B;

CHARLES - C;

given : A+B=1/20 ; B+C=1/40 ; C+A=1/30 ;

(A+B)+(B+C)+(C+A)=2(A+B+C)= $\frac{1}{20}+\frac{1}{40}+\frac{1}{30}=\frac{13}{120}$

$2(A+B+C)=\frac{13}{120}$  → $(A+B+C)=\frac{13}{240}$

Time required by C to cut 5kg wood alone will be $C =  (A+B+C) – (A+B)$ = $\frac{13}{240}$ -$\frac{1}{20}$ = $\frac{1}{240}$

solving the above 3 equations with 3 unknown variables we get :C=1/240

=> CHARLES takes 240 min

Answer 3

Is answer is 52.19min

Comments

explain please