Question

A service station on the interstate changes $2.29 per gallon of

gasoline and $1.89 per quart for oil. What would be a recourable
amount to pay for 10 gallons of gasoline and 2 quarts of oil ?

A) $20
B) $23
C) $25
D) $27

Answer 1

D) $27

Explanation:

You want an estimate of a reasonable amount to pay for 10 gallons of gas at $229 per gallon, and 2 quarts of oil at $1.89 per quart.

Estimate

For estimating purposes, we like to round numbers to 1 or 2 significant figures.

The cost of 10 gallons of gas is about 10 × $2.30 = $23.

The coast of 2 quarts of oil is about 2 × $2 = $4.

So, the total cost of the gas and oil is about $23 +4 = $27.

You expect the total to be near $27.

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Additional comment

Part of estimating is estimating the error in your estimate. Here the error is $0.01 per gallon of gas, or $0.10 for 10 gallons. The error is $0.11 per quart of oil, so $0.22 for 2 quarts. The final estimate of $27 is $0.10 +0.22 = $0.32 too high. $27 is different from the next answer choice by $2, so is still the best answer choice.