Question
Three pipes P, Q and R can fill a cistern in 40 minutes,
80 minutes and 120 minutes, respectively. Initially, all the pipes are opened. After how much time (in minutes) should the pipes Q and R be turned off so that the cistern will be completely filled in just half an hour?Solution
Assume total work = 240 units (LCM of 40, 80, 120).
Efficiencies: P = 6 units/min, Q = 3 units/min, R = 2 units/min. Let Q and R be turned off after x minutes. Work in first x minutes = (6 + 3 + 2 ) × x = 11x Work in remaining 30 − x minutes by P = 6(30 − x) 11 x + 6 ( 30 − x ) = 240 ⇒ 11 x + 180 − 6 x = 240 ⇒ 5 x = 60 ⇒ x = 12
If a3Â + 3a2Â + 9a = 1, then what is the value of a3Â + (3/a)?
The value of x which satisfies the equation (x+a2+2c2) / (b+c) + (x+b2 +2a2) / (c+a) + (x+c+2b2) ...
10 women and 12 men complete a certain piece of work in 30 days, if each women takes thrice the time taken by a man to finish the work.
Quanti...
The value of the expression (1 + sec22° + cot68°)(1 – cosec22° + tan68°) is
If the nine-digit number 43x1145y2 is divisible by 88, then the value of (3x — 2y), for the smallest value of y, is:
If 2cos2 Ɵ – 5cos Ɵ + 2 = 0,00 < Ɵ < 900 , then the value of (cosec Ɵ + cot Ɵ) is :
Find x, given 5 (√5)x+6 = (√5)2x+7 :
If 0 ≤ θ ≤ 90°, and sec107 θ + cos107 θ = 2, then. (secθ + cosθ) is equal to:
The expression of (cot θ + cosec θ −1) / (cot θ − cosec θ+1) is equal to
If α and β are the roots of equation x2 – x + 1 = 0, then which equation will have roots α3 and β3?
...
Relevant for Exams:
