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, 2020

Algebra Difficulty 1.4 Junior Find the answer Canada

Harriet ran a 1000 m course in 380 seconds. She ran the first 720 m of the course at a constant speed of 3 m/s. She ran the remaining part of the course at a constant speed of $v$ m/s. What is the value of $v$ ?

$2$
$1.5$
$3$
$1$
$4.5$

Your answer

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Solution

Since Harriet ran 720 m at 3 m/s, then this segment took her $\text{720 m 3 m/s = 240 s}$ .
In total, Harriet ran 1000 m in 380 s, so the remaining part of the course was a distance of $\text{1000 m - 720 m = 280 m}$ which she ran in $\text{380 s - 240 s = 140 s}$ .
Since she ran this section at a constant speed of $v$ m/s, then $\text{280 m 140 s = v m/s}$ which means that $v=2$ .

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Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project.