A percentage is essentially a fraction, but lazily written. Think of a percent as 25/100, or 0.25.
Now multiply the two.
0.25x5/8.
We need to convert 5/8 to a decimal, which is 0.625.
0.25x0.625=0.15625.
Now convert the decimal to a fraction, which is 5/32.
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hope it helps