Twice the larger of two numbers is three more than five times the smaller and…
2017
Twice the larger of two numbers is three more than five times the smaller and the sum of four times the larger and three times the smaller is 71. What are the numbers?
- A.
43, 8
- B.
11, 9
- C.
14, 5
- D.
17, 1
Attempted by 2 students.
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Correct answer: C
To solve a word problem describing two related unknown quantities, translate each verbal relationship into a linear equation in two variables, then solve the resulting system by substitution or elimination.
Let L denote the larger number and S denote the smaller number.
"Twice the larger is three more than five times the smaller" translates to 2L = 5S + 3.
"The sum of four times the larger and three times the smaller is 71" translates to 4L + 3S = 71.
Multiply the first equation by 2: 4L = 10S + 6.
Substitute this into the second equation: (10S + 6) + 3S = 71, which gives 13S + 6 = 71.
Solve for S: 13S = 65, so S = 5.
Substitute S = 5 into 2L = 5S + 3: 2L = 28, so L = 14.
Verify both conditions with L = 14 and S = 5: twice the larger, 2 x 14 = 28, equals five times the smaller plus three, 5 x 5 + 3 = 28. Also, four times the larger plus three times the smaller, 4 x 14 + 3 x 5 = 56 + 15 = 71, matches the given total. Both equations are satisfied, so the numbers are 14 and 5.