WAEC 2021 · Paper 2 · Q2

Linear & simultaneous equations
Commercial arithmetic

The distance between two ports $M$ and $N$ is $2100\text{ km}$ . Two ships travel towards each other, one leaving port $M$ at $20\text{ km/h}$ and, at the same time, another from port $N$ at $15\text{ km/h}$ . How:

(a)
long will it take the two ships to meet?
(b)
far will they be from port $M$ when they meet?

Worked solution (try it first)

(a)

The ships move towards each other, so the gap between them closes at $20 + 15 = 35\text{ km/h}$ .
Let them meet after $t$ hours: $35t = 2100$ , so $t = 60$ .
They meet after 60 hours.

(b)

In 60 hours the ship from $M$ travels $20 \times 60 = 1200\text{ km}$ .
They meet 1200 km from port $M$ .
(Check: the other ship travels $15 \times 60 = 900$ km, and $1200 + 900 = 2100$ ✓.)

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