PSLE Kathy 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 244 cm. How many oval rings did Kathy 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 = 244
Number of oval rings x 10 = 244 - 4
Number of oval rings x 10 = 240
Number of oval rings = 240 ÷ 10
Number of oval rings = 24
Number of oval rings that Kathy hung altogether = 24
Answer(s): (a) 34 cm; (b) 24