PSLE
Xylia hung some identical oval rings vertically. The thickness of each oval ring was 1 cm. The figure shows how the oval rings are connected.

1. What was the distance from the top of the 1st oval ring to the bottom of the 4th oval ring?
2. The distance from the top of the 1st ring to the bottom of the last ring was 122 cm. How many oval rings did Xylia hang altogether?

(a)
Distance of 1 oval ring = 10 cm = 1 x 8 + 2
Distance of 2 oval rings = 18 cm = 2 x 8 + 2
Distance of 3 oval rings = 26 cm = 3 x 8 + 2

Distance from the top of the 1st oval ring to the bottom of the 4th oval ring = 26 cm

(b)
Formula
Distance from the top of the 1st oval ring to the bottom of the last oval ring = Number of oval rings x 8 + 2

Number of oval rings x 8 + 2 = 122
Number of oval rings x 8 = 122 - 2
Number of oval rings x 8 = 120
Number of oval rings = 120 ÷ 8
Number of oval rings = 15

Number of oval rings that Xylia hung altogether = 15

Answer(s): (a) 26 cm; (b) 15