PSLE Abi 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 4th oval ring?
- The distance from the top of the 1st ring to the bottom of the last ring was 204 cm. How many oval rings did Abi hang altogether?
(a)
Distance of 1 oval ring = 14 cm = 1 x 10 + 4
Distance of 2 oval rings = 24 cm = 2 x 10 + 4
Distance of 3 oval rings = 34 cm = 3 x 10 + 4
Distance from the top of the 1st oval ring to the bottom of the 4th oval ring = 34 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 + 4
Number of oval rings x 10 + 4 = 204
Number of oval rings x 10 = 204 - 4
Number of oval rings x 10 = 200
Number of oval rings = 200 ÷ 10
Number of oval rings = 20
Number of oval rings that Abi hung altogether = 20
Answer(s): (a) 34 cm; (b) 20