PSLE Emily 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 235 cm. How many oval rings did Emily hang altogether?
(a)
Distance of 1 oval ring = 15 cm = 1 x 11 + 4
Distance of 2 oval rings = 26 cm = 2 x 11 + 4
Distance of 3 oval rings = 37 cm = 3 x 11 + 4
Distance from the top of the 1st oval ring to the bottom of the 4th oval ring = 37 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 11 + 4
Number of oval rings x 11 + 4 = 235
Number of oval rings x 11 = 235 - 4
Number of oval rings x 11 = 231
Number of oval rings = 231 ÷ 11
Number of oval rings = 21
Number of oval rings that Emily hung altogether = 21
Answer(s): (a) 37 cm; (b) 21