PSLE Lynn hung some identical oval rings vertically. The thickness of each oval ring was 2 cm. The figure shows how the oval rings are connected.
- What was the distance from the top of the 1st oval ring to the bottom of the 6th oval ring?
- The distance from the top of the 1st ring to the bottom of the last ring was 162 cm. How many oval rings did Lynn hang altogether?
(a)
Distance of 1 oval ring = 12 cm = 1 x 10 + 2
Distance of 2 oval rings = 22 cm = 2 x 10 + 2
Distance of 3 oval rings = 32 cm = 3 x 10 + 2
Distance from the top of the 1st oval ring to the bottom of the 6th oval ring = 32 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 10 + 2
Number of oval rings x 10 + 2 = 162
Number of oval rings x 10 = 162 - 2
Number of oval rings x 10 = 160
Number of oval rings = 160 ÷ 10
Number of oval rings = 16
Number of oval rings that Lynn hung altogether = 16
Answer(s): (a) 32 cm; (b) 16