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John and Mary have some marbles. The total number of marbles with John and Mary is 7575 times the ratio of the number of marbles with John to that with Mary. If Mary has 3030 marbles, find the number of marbles with John.\newline(A) 2020 \newline(B) 3030 \newline(C) 4545 \newline(D) 5050

Full solution

Q. John and Mary have some marbles. The total number of marbles with John and Mary is 7575 times the ratio of the number of marbles with John to that with Mary. If Mary has 3030 marbles, find the number of marbles with John.\newline(A) 2020 \newline(B) 3030 \newline(C) 4545 \newline(D) 5050
  1. Define Variables: Let's denote the number of marbles with John as JJ and the number of marbles with Mary as MM. According to the problem, MM is given as 3030. The total number of marbles is 7575 times the ratio of the number of marbles with John to that with Mary. This can be written as:\newlineTotal number of marbles = J+M=75×(JM)J + M = 75 \times (\frac{J}{M})
  2. Substitute Value: We know that M=30M = 30, so we can substitute this value into the equation:\newlineJ+30=75×(J30)J + 30 = 75 \times (\frac{J}{30})
  3. Multiply Equation: To solve for JJ, we need to get rid of the fraction. We can do this by multiplying both sides of the equation by 3030:30×(J+30)=30×75×(J30)30 \times (J + 30) = 30 \times 75 \times \left(\frac{J}{30}\right)
  4. Simplify Equation: Simplifying both sides of the equation, we get: 30J+900=75J30J + 900 = 75J
  5. Isolate Variable: Now, we need to isolate JJ on one side of the equation. We can do this by subtracting 30J30J from both sides:\newline30J+90030J=75J30J30J + 900 - 30J = 75J - 30J
  6. Divide to Solve: This simplifies to: 900=45J900 = 45J
  7. Divide to Solve: This simplifies to:\newline900=45J900 = 45JTo find JJ, we divide both sides of the equation by 4545:\newline90045=45J45\frac{900}{45} = \frac{45J}{45}
  8. Divide to Solve: This simplifies to:\newline900=45J900 = 45JTo find JJ, we divide both sides of the equation by 4545:\newline90045=45J45\frac{900}{45} = \frac{45J}{45}Solving for JJ, we get:\newlineJ=90045J = \frac{900}{45}\newlineJ=20J = 20