Answer:
80 mm
Explanation:
1/p + 1/20 = 1/16
Subtract 1/20 from both sides
1/p = 1/16 - 1/20
Use 160 as common denominator
1/p = 10/160 - 8/160
1/p = 2/160
1/p = 1/80
Cross multiply
80 = p
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