PSLE Kylie hung some identical rings vertically. The thickness of each ring was 1 cm. The figure shows how the rings are connected.
- What was the distance from the top of the 1st ring to the bottom of the 4th ring?
- The distance from the top of the 1st ring to the bottom of the last ring was 105 cm. How many rings did Kylie hang altogether?
(a)
Distance of 1 ring = 14 cm = 1 x 13 + 1
Distance of 2 rings = 27 cm = 2 x 13 + 1
Distance of 3 rings = 40 cm = 3 x 13 + 1
Distance from the top of the 1st ring to the bottom of the 4th ring
= 4 x 13 + 1
= 53 cm
(b)
Formula
Distance from the top of the 1st ring to the bottom of the last ring = Number of rings x 13 + 1
Number of rings x 13 + 1 = 105
Number of rings x 13 = 105 - 1
Number of rings x 13 = 104
Number of rings = 104 ÷ 13
Number of rings = 8
Number of rings that Kylie hung altogether = 8
Answer(s): (a) 53 cm; (b) 8