PSLE Natalie 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 200 cm. How many oval rings did Natalie hang altogether?
(a)
Distance of 1 oval ring = 13 cm = 1 x 11 + 2
Distance of 2 oval rings = 24 cm = 2 x 11 + 2
Distance of 3 oval rings = 35 cm = 3 x 11 + 2
Distance from the top of the 1st oval ring to the bottom of the 4th oval ring = 35 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 + 2
Number of oval rings x 11 + 2 = 200
Number of oval rings x 11 = 200 - 2
Number of oval rings x 11 = 198
Number of oval rings = 198 ÷ 11
Number of oval rings = 18
Number of oval rings that Natalie hung altogether = 18
Answer(s): (a) 35 cm; (b) 18