Math Problem Statement

A and B can do a piece of work in 30 days, while B and C can do the same work in 24 days and C and A in 20 days. They all work together for 10 days, after that B and C left the work. If they got Rs 7500 for that work then how much A get more than C?

Solution

Let's solve the problem step by step.

Step 1: Define the rates of work

Let:

  • A's rate of work = AA (work per day)
  • B's rate of work = BB
  • C's rate of work = CC

From the given information, we can write the following equations:

  • A and B together can complete the work in 30 days, so: A + B = \frac{1}{30} \quad \text{(This means A and B together can complete \frac{1}{30} of the work in 1 day.)}
  • B and C together can complete the work in 24 days, so: B+C=124B + C = \frac{1}{24}
  • C and A together can complete the work in 20 days, so: C+A=120C + A = \frac{1}{20}

Step 2: Find individual work rates

We have three equations:

  1. A+B=130A + B = \frac{1}{30}
  2. B+C=124B + C = \frac{1}{24}
  3. C+A=120C + A = \frac{1}{20}

To find AA, BB, and CC, let's add all three equations: (A+B)+(B+C)+(C+A)=130+124+120(A + B) + (B + C) + (C + A) = \frac{1}{30} + \frac{1}{24} + \frac{1}{20} This simplifies to: 2(A+B+C)=130+124+1202(A + B + C) = \frac{1}{30} + \frac{1}{24} + \frac{1}{20}

Now, find the common denominator of 30, 24, and 20. The least common denominator (LCD) is 120, so: 130=4120,124=5120,120=6120\frac{1}{30} = \frac{4}{120}, \quad \frac{1}{24} = \frac{5}{120}, \quad \frac{1}{20} = \frac{6}{120} Thus, 2(A+B+C)=4+5+6120=15120=182(A + B + C) = \frac{4 + 5 + 6}{120} = \frac{15}{120} = \frac{1}{8} Dividing both sides by 2: A+B+C=116A + B + C = \frac{1}{16}

Step 3: Solve for individual rates

Now, use the value A+B+C=116A + B + C = \frac{1}{16} in the original equations to find each person's rate:

  1. A+B=130A + B = \frac{1}{30}
  2. B+C=124B + C = \frac{1}{24}
  3. C+A=120C + A = \frac{1}{20}

From A+B+C=116A + B + C = \frac{1}{16}, we know: A=(A+B+C)(B+C)=116124=348248=148A = (A + B + C) - (B + C) = \frac{1}{16} - \frac{1}{24} = \frac{3}{48} - \frac{2}{48} = \frac{1}{48} So, A=148A = \frac{1}{48} (A completes 148\frac{1}{48} of the work in 1 day).

Now, use this to find BB and CC:

  • From A+B=130A + B = \frac{1}{30}, we get: B=130148=85240=3240=180B = \frac{1}{30} - \frac{1}{48} = \frac{8 - 5}{240} = \frac{3}{240} = \frac{1}{80}
  • From C+A=120C + A = \frac{1}{20}, we get: C=120148=125240=7240=7240C = \frac{1}{20} - \frac{1}{48} = \frac{12 - 5}{240} = \frac{7}{240} = \frac{7}{240}

Thus, A=148,B=180,C=180A = \frac{1}{48}, B = \frac{1}{80}, C = \frac{1}{80}.

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Math Problem Analysis

Mathematical Concepts

Work and Time
Algebra
Rates of Work

Formulas

A + B = 1/30 (combined work rate of A and B)
B + C = 1/24 (combined work rate of B and C)
C + A = 1/20 (combined work rate of C and A)
A + B + C = 1/16 (total work rate)

Theorems

Work Rate Theorem

Suitable Grade Level

Grades 9-12