PSLE Wendy 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 127 cm. How many oval rings did Wendy hang altogether?
(a)
Distance of 1 oval ring = 10 cm = 1 x 9 + 1
Distance of 2 oval rings = 19 cm = 2 x 9 + 1
Distance of 3 oval rings = 28 cm = 3 x 9 + 1
Distance from the top of the 1st oval ring to the bottom of the 5th oval ring = 28 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 9 + 1
Number of oval rings x 9 + 1 = 127
Number of oval rings x 9 = 127 - 1
Number of oval rings x 9 = 126
Number of oval rings = 126 ÷ 9
Number of oval rings = 14
Number of oval rings that Wendy hung altogether = 14
Answer(s): (a) 28 cm; (b) 14