PSLE Vanessa 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 188 cm. How many rings did Vanessa hang altogether?
(a)
Distance of 1 ring = 12 cm = 1 x 11 + 1
Distance of 2 rings = 23 cm = 2 x 11 + 1
Distance of 3 rings = 34 cm = 3 x 11 + 1
Distance from the top of the 1st ring to the bottom of the 4th ring
= 4 x 11 + 1
= 45 cm
(b)
Formula
Distance from the top of the 1st ring to the bottom of the last ring = Number of rings x 11 + 1
Number of rings x 11 + 1 = 188
Number of rings x 11 = 188 - 1
Number of rings x 11 = 187
Number of rings = 187 ÷ 11
Number of rings = 17
Number of rings that Vanessa hung altogether = 17
Answer(s): (a) 45 cm; (b) 17