This is a  Time Speed Distance question.

52.5 + 70u = 100u

52.5 = 100u – 70u

30u = 52.5

1u = 52.5 ÷ 30 = 1.75 h = 1 h 45 min

1h 45 min + 45 min = 2 h 30 min

9 h 30 min + 2 h 30 min = 12 h = 12.00 pm

Note

10 h 15 min – 9 h 30 min = 45 min

45 min = 45/ 60 h

Mr. Pek, 

52.5 + 70u = 100u — I do not understand this step. May I know how 52.5+70u = 100u ?. Please explain.  

Thanks

RQ started first for 45 min = 45/60 hr

RQ2 is the same time movement with J.

Since we do not know how long they meet, we put it as lu hour later.

So total distance for RQ = 52.5 + 70u

Total distance for J = 100u

When they meet, their distance are equal.

RQ started first for 45 min = 45/60 hr

RQ2 is the same time movement with J.

Since we do not know how long they meet, we put it as lu hour later.

So total distance for RQ = 52.5 + 70u

Total distance for J = 100u

When they meet, their distance are equal.

10h15m – 9h30m = 45min = 0.75h
0.75 x 70 = 52.5
100 – 70 = 30
52.5 / 30 = 1.75h = 1h45m
10h15m + 1h45m = 12h = 12 p.m. as the answer

1. Rui Qi has a 45min head start, Find how far ahead she is when Jaclyn began her journey,
Distance = 70 X 45/60 = 52.5km.

2. Jocelyn is 30km/h faster than Rui Qi. So to catch up with Rui Qi while she is still traveling, relatively speaking Jocelyn is catching up at 30km/h over 52.5km.

Time taken by Jocelyn to catch up = 52.5/30 = 1.75 hr or 1hr 45min.

Time when she caught up with Rui Qi will be 1hr 45mins from 10:15am – > i.e. 12pm.