The given table shows the number of minutes Jalen talks on his mobile phone and the cost of the phone calls. Jalen’s Mobile Phone Cost Number of minutes, x 150 220 250 275 Cost, y 7 point 5 0 dollars 11 point 0 0 dollars 12 point 5 0 dollars 13 point 7 5 dollars If the cost varies directly with the number of minutes Jalen talks on the phone, which equation represents the variation?
Answer
A
y is equal to 157 point 5 x
B
y is equal to 20 x
C
y is equal to 1125 x
D
y is equal to 0 point 0 5 x
Explanation
For direct variation, the cost is y = kx, where k is the cost per minute. Using 150 minutes and $7.50 gives k = 7.50 ÷ 150 = 0.05 dollars per minute. So the equation is y = 0.05x, which is choice D.
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