Answer each part below using only mental math, and describe your method. a. If 39 is 1% of a number, what is that number? How did you find your answer? b. If 39 is 10% of a number, what is that number? How did you find your answer? c. If 39 is 5% of a number, what is that number? How did you find your answer? d. If 39 is 15% of a number, what is that number? How did you find your answer?

Step-by-step explanation:

Given:  39 = 0.01n

Move the decimal point on each side two places to the right:  3900 = n

first, we define the variables:

x: number of years after 1950

f (x): amount of vinyl sold.

then, with the variables defined, we have:

68594 vinyl records were sold in 1958 > f (8) = 68594

91299 vinyl records were sold in 1961 > f (11) = 91299

38720 vinyl records were sold in 1952 > f (2) = 38720

161743 vinyl records were sold in 1967 > f (17) = 161743

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step-by-step explanation: