PSLE Xylia 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 162 cm. How many oval rings did Xylia hang altogether?
(a)
Distance of 1 oval ring = 10 cm = 1 x 8 + 2
Distance of 2 oval rings = 18 cm = 2 x 8 + 2
Distance of 3 oval rings = 26 cm = 3 x 8 + 2
Distance from the top of the 1st oval ring to the bottom of the 4th oval ring = 26 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 + 2
Number of oval rings x 8 + 2 = 162
Number of oval rings x 8 = 162 - 2
Number of oval rings x 8 = 160
Number of oval rings = 160 ÷ 8
Number of oval rings = 20
Number of oval rings that Xylia hung altogether = 20
Answer(s): (a) 26 cm; (b) 20