If y varies directly as x and y = 70 when x = 10, find y when x = 36.
252
2,520
25,200
5.14

252

Step-by-step explanation:

y varies directly with x means y=kx where k is a constant.

A constant means it never changes no matter what the point (x,y) they give.

So y=kx means y/x=k (I just divided both sides by x here).

So we have the following proportion to solve:

70/10 reduces to 7:

Multiply both sides by 36:

Simplify left hand side:

So y is 252 when x is 36.

the largest number of the four options is 1.8 x 10-2

you have it in scientific notation.

1.80 x 10-6   = 0.00000180

1.80 x 10-4   = 0.000180 (bigger, or "less small", than the former one)

so

1.8 x 10-2       = 0.0180. as you see. the "less small", or the biggest one of them all.

as you have negative exponent, it means you are dividing 1.8 by 100 (i.e. moving the dot towards left, two times).

if you had positive exponent for the scientific notation, power of tenths, you would be multiplying times 100 (moving the dot towards right) as below:

1.8 x (10)2 = 180

so. if you have negative exponent in scientific notation, move the dot toward left. if it is positive, toward right as many times the exponent tells you.

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step-by-step explanation: