PSLE Jeremy uses toothpicks to form figures that follow a pattern. The first four figures are shown.
- The table shows the number of toothpicks used for each figure. Complete the table for Figure 7 and Figure 8. Give your answers in numbers. (Eg 1, 2)
- What is the difference in the number of toothpicks that Jeremy would use for Figure 15 and Figure 17?
- How many toothpicks would he use for Figure 18?
(a)
Number of toothpicks used:
Figure 1: 15 = 11 + 4 x 1Figure 2: 18 = 10 + 4 x 2Figure 3: 23 = 11 + 4 x 3Figure 4: 26 = 10 + 4 x 4The formula for the total number of toothpicks used is different for odd-numbered patterns and even-numbered patterns.
Number of toothpicks for odd-numbered figure = 11 + 4 x Figure number
Number of toothpicks for even-numbered figure = 10 + 4 x Figure numberNumber of toothpicks used for Figure 7
= 11 + 4 x 7
= 11 + 28
= 39
Number of toothpicks used for Figure 8
= 10 + 4 x 8
= 10 + 32
= 42
(b)
Since every 2 jumps has the same increase,
difference in the number of toothpicks for Figure 15 and 17 = 8
(c)
Figure 18 is an even number.
Number of toothpicks that Jeremy would use for Figure 18
= 10 + 4 x Figure number
= 10 + 4 x 18
= 10 + 72
= 82
Answer(s): (a) 39, 42; (b) 8; (c) 82
