How to do work done questions in maths class 10?
Answers
Answer:
Problems on Time and Work :
1.
days, i.e., 6²/₃ days.
Hence both can finish the work in 6²/₃ days.
2. A and B together can do a piece of work in 15 days, while B alone can finish it 20 days. In how many days can A alone finish the work?
Solution:
Time taken by (A + B) to finish the work = 15 days.
Time taken by B alone to finish the work 20 days.
(A + B)’s 1 day’s work = ¹/₁₅
and B’s 1 day’s work = ¹/₂₀
A’s 1 day’s work = {(A + B)’s 1 day’s work} - {B’s 1 day’s work}
= (¹/₁₅ - ¹/₂₀) = (4 - 3)/60 = ¹/₆₀
Therefore, A alone can finish the work in 60 days.
3. A can do a piece of work in 25 days and B can finish it in 20 days. They work together for 5 days and then A leaves. In how many days will B finish the remaining work?
Solution:
= (¹/₁₀ - ¹/₁₅) = ¹/₃₀
Hence, A alone can finish the work in 30 days.
B’s 1 day’s work
{(A + B + C)’s 1 day’s work} - {(C + A)’s 1 day’s work}
(¹/₁₀ – ¹/₂₀) = ¹/₂₀ Hence, B alone can finish the work in 20 days.
C’s 1 days work
= {(A + B + C)’s 1 day’s work} - {(A + B)’s 1 day’s work}
= (¹/₁₀ – ¹/₁₂) = ¹/₆₀
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