PSLE Marion 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 6th oval ring?
- The distance from the top of the 1st ring to the bottom of the last ring was 169 cm. How many oval rings did Marion hang altogether?
(a)
Distance of 1 oval ring = 9 cm = 1 x 8 + 1
Distance of 2 oval rings = 17 cm = 2 x 8 + 1
Distance of 3 oval rings = 25 cm = 3 x 8 + 1
Distance from the top of the 1st oval ring to the bottom of the 6th oval ring = 25 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 + 1
Number of oval rings x 8 + 1 = 169
Number of oval rings x 8 = 169 - 1
Number of oval rings x 8 = 168
Number of oval rings = 168 ÷ 8
Number of oval rings = 21
Number of oval rings that Marion hung altogether = 21
Answer(s): (a) 25 cm; (b) 21