AnswersPrecalculusCramer's Rule — Unit testQuestion 3
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Cramer's Rule — Unit test

Question 3 • Precalculus

The table below shows the number of house calls three different plumbers made on three different days. Number of House Calls Plumber APlumber BPlumber CMonday288Tuesday4710Wednesday399The total amount of money earned by all three plumbers on Monday was $1,400. On Tuesday they earned a total of $1,660, and on Wednesday, they earned a total of $1,650. On Thursday, Plumber A made four house calls, Plumber B made six house calls, and Plumber C made three house calls. How much total money is earned on Thursday?

Answer
A
$250
B
$1,060
C
$1,090
D
$1,130

Explanation

Let x, y, and z be the dollars each plumber earns per house call. The Monday and Wednesday totals give 2x + 8y + 8z = 1,400 and 3x + 9y + 9z = 1,650, which simplify to x + 4y + 4z = 700 and x + 3y + 3z = 550. Subtracting shows y + z = 150, and then x = 100. Using Tuesday’s total gives 7y + 10z = 1,260; together with y + z = 150, this gives y = 80 and z = 70. On Thursday the total is 4(100) + 6(80) + 3(70) = $1,090, choice C.

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