Exercise: Ratios & Proportions

Questions for: Sharing & Comparison

Three friends, John, Kevin, and Liam, shared a total prize money. John received 3/5 of what Kevin received. Liam received 1/2 of what John and Kevin received together. If Kevin received 300 more than John, what was the total prize money?

A: 1800
B: 1575
C: 1425
D: 1950
Answer: A

✅ First, set up equations based on the given conditions: J = (3/5)K, L = (1/2)(J + K), and K = J + 300.

Substitute K = J + 300 into the first equation to solve for J: J = (3/5)(J + 300) which simplifies to 5J = 3J + 900, yielding 2J = 900, so J = 450.

Then, find Kevin's share: K = J + 300 = 450 + 300 = 750.

Next, calculate Liam's share: L = (1/2)(J + K) = (1/2)(450 + 750) = (1/2)(1200) = 600.

Finally, sum the individual shares to find the total prize money: Total = J + K + L = 450 + 750 + 600 = 1800.

❌ Option B ($1575) is incorrect because it might result from calculating Liam's share as half of Kevin's share only (L = 1/2 * K = 1/2 * 750 = 375), leading to a total of 450 + 750 + 375 = 1575.

❌ Option C ($1425) is incorrect because it might result from calculating Liam's share as half of John's share only (L = 1/2 * J = 1/2 * 450 = 225), leading to a total of 450 + 750 + 225 = 1425.

❌ Option D ($1950) is incorrect because it could arise if Liam's share was mistakenly assumed to be equal to Kevin's share (L = K = 750), leading to a total of 450 + 750 + 750 = 1950.

Alex, Ben, and Chloe shared a total prize money. Alex received 3/5 of what Ben and Chloe together received. Ben received 2/5 of what Alex and Chloe together received. If Chloe received $1200 less than Alex, what was the total prize money?

A: $33,600
B: $16,800
C: $24,000
D: $31,200
Answer: A

✅ Let the total prize money be T. Let A, B, and C be the shares of Alex, Ben, and Chloe, respectively. So, A + B + C = T.

From the first condition, "Alex received 3/5 of what Ben and Chloe together received": A = (3/5)(B + C). This implies 5A = 3B + 3C. Since B + C = T - A, we have 5A = 3(T - A), which simplifies to 5A = 3T - 3A, so 8A = 3T, meaning A = (3/8)T.

From the second condition, "Ben received 2/5 of what Alex and Chloe together received": B = (2/5)(A + C). This implies 5B = 2A + 2C. Since A + C = T - B, we have 5B = 2(T - B), which simplifies to 5B = 2T - 2B, so 7B = 2T, meaning B = (2/7)T.

Now, we find Chloe's share (C) as a fraction of the total: C = T - A - B = T - (3/8)T - (2/7)T. To combine these, find a common denominator for 8 and 7, which is 56. C = (56/56)T - (21/56)T - (16/56)T = (56 - 21 - 16)/56 T = (19/56)T.

The third condition states, "Chloe received $1200 less than Alex", which means A - C = 1200. Substitute the fractional values: (3/8)T - (19/56)T = 1200. Convert (3/8)T to a fraction with denominator 56: (21/56)T - (19/56)T = 1200.

This simplifies to (2/56)T = 1200, or (1/28)T = 1200. Therefore, T = 1200 × 28 = $33,600.

Formula(s) used:

  • Ratio: a:b = a/b
  • Proportion: a/b = c/d
  • Sharing formula (derived): If an individual's share A is k times the sum of other shares, A = k(B+C), and total T = A+B+C, then A = (k/(1+k))T.

❌ Option B is incorrect. This would result if the fractional difference was mistakenly calculated as 1/14 of the total instead of 1/28 (i.e., 1200 × 14 = 16800).

❌ Option C is incorrect. This value might arise from various calculation errors, such as mistakenly using 1/20 as the fraction of the total for the $1200 difference, which would give 1200 × 20 = 24000.

❌ Option D is incorrect. This value of $31,200 would occur if the multiplier was 26 instead of 28 (1200 × 26 = 31200), possibly from an arithmetic error during the simplification of fractions or solving the equation.

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