PSLE Hazel hung some identical oval rings vertically. The thickness of each oval ring was 1 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 5th oval ring?
- The distance from the top of the 1st ring to the bottom of the last ring was 232 cm. How many oval rings did Hazel 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 5th 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 = 232
Number of oval rings x 10 = 232 - 2
Number of oval rings x 10 = 230
Number of oval rings = 230 ÷ 10
Number of oval rings = 23
Number of oval rings that Hazel hung altogether = 23
Answer(s): (a) 32 cm; (b) 23