SOLUTION: If y is directly proportional to the square root of x and y = −32 when x = 400, find y if x = 160000. (Round off your answer to the nearest hundredth.)

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Question 1009040: If y is directly proportional to the square root of x and y = −32 when x = 400, find y if x = 160000. (Round off your answer to the nearest hundredth.)
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

If y+is directly proportional to the sqrt%28x+%29, we have
y+=k%2Asqrt%28x+%29
and if y+=+-32 when x+=+400, we can find a constant k
-32+=k%2Asqrt%28400+%29
-32+=k%2A20+
k=+-32%2F20
k=+-8%2F5
so, equation is: y+=+%28-8%2F5%29%2Asqrt%28x+%29
if x+=+160000, then
y+=+%28-8%2F5%29%2Asqrt%28160000+%29
y+=+%28-8%2Fcross%285%29%29%2Across%28400%2980+
y+=+-8%2A80+
y+=+-640+