**Q18**.

Let there be 40u passengers at Pasir Ris (PR).

At Tampines (T), 2/5 alighted, 80 boarded. So, at T: 24u + 80

At Simei (S), 223 alighted, 38 boarded, so at S: 24u + 80 - 223 + 38 = 24u - 105,

which is 3/8 of no. at T, and this is 3/8 x (24u + 80) = 9u + 30

So, 9u + 30 = 24u - 105

That is, 15u = 135

So that, 1u = 9

(a) There were 9 x 9 + 30 = **111** **people** when it left S.

[check: 24 x 9 - 105 = 111 ]

(b) When it left PR, there were 40 x 9 = **360** **people**.

**Q15.**

[it's difficult to redraw figure here, but hope you can follow...]

Call the unshaded region 'between' regions X and Y region A (unshaded part between arc and longest edge of isosceles triangle with equal sides of 10 cm)

Then, areas of.... X + A = area of quadrant - 0.5 x 10cm x 10 cm = quadrant - 50 ...........[1]

( I'm leaving out unit for easy typing)

And, areas of.......Y + A = 0.5 x 5 x 5 = 12.5..................................[2]

From [1] - [2]:

X - Y = quadrant - 50 - 12.5 = 0.25 x <pi> x 10 x 10 - 62.5 = 16.0398 = **16**.**04** **cm2** (2 d.p.)

Hope this is clear and helpful, Cheerio!