Simplify (0.25 × 0.25 - 0.15 × 0.15)/(0.25 - 0.15).

Simplification & Approximation · Question 31 of 71

Question 31

MediumOriginal question

Simplify $\dfrac{0.25 \times 0.25 - 0.15 \times 0.15}{0.25 - 0.15}$ .

0.04Correct answerYour answer0.1Correct answerYour answer0.4Correct answerYour answer4Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer C

Correct answer: C

The numerator is $a^2 - b^2$ with $a = 0.25$ , $b = 0.15$ , and $a^2 - b^2 = (a - b)(a + b)$ .
Cancelling $(a - b)$ leaves $a + b = 0.25 + 0.15 = 0.4$ .

Worth noting

Direct working: $0.0625 - 0.0225 = 0.04$ , and $0.04 \div 0.1 = 0.4$ . Stopping at the numerator gives 0.04.

Ten questions from Simplification & Approximation, at your own pace.

Ten questions from Simplification & Approximation, at your own pace.