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prealgebra intermediate

Problem

If

1 0^{2 y} = 25

, then

1 0^{- y}

equals:

(A)

- \frac{1}{5}

(B)

\frac{1}{625}

(C)

\frac{1}{50}

(D)

\frac{1}{25}

(E)

\frac{1}{5}

Solution

If

1 0^{2 y} = (1 0^{y})^{2} = 25

, then

1 0^{y} = 5

and

1 0^{- y} = \frac{1}{5} .

Final answer

E