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Twelfths rounded

Mental mathMedium

A pipeline completes $\frac{5}{12}$ of its jobs on time. Give this as a decimal rounded to $3$ decimal places.

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Hint

Use $\frac{1}{12}$ as a third of a quarter.

Solution

$\frac{1}{4} = 0.25$ , so $\frac{1}{12} = 0.25 \div 3$ .
That is $0.08333 \dots$ , so $\frac{5}{12} = 5 \times 0.08333 \dots = 0.41666 \dots$ .
Rounding to $3$ decimal places moves the last digit up.
The value is $0.417$ .

Answer: $\approx 0.417$