Question

Two pipes take x minutes and (x+3) minutes respectively to fill a cistern. If together they fill the cistern in 3/1/13 ( it us in mixed fraction) minutes , find the value of x.

Answer 1

so...time taken by 1st pipe to fill the cistern in 1 min=1/x...and the time taken by the second pipe to fill the cistern in 1 min=1/x+3...so..time taken by both the pipes when you they are running together=1/40/13=13/40...so 1/x+1/x+3=13/40=>120+80x=13x^2+39x=>13x^2-41x-120=0=>13x^2-65x+24x-120=0=>(13x+24)(x-5)=0=>x=5 and x=-24/13..so we know time cannot be negative soo..x=5mins(ans)