PSLE The first 15 numbers of a number pattern are given.
8, 4, 1, 6, 8, 4, 1, 6, 8, 4, 1, 6, 8, 4, 1, ...
- What is the 990th number?
- What is the sum of the first 123 numbers?
(a)
Each set of numbers: 8, 4, 1, 6
Each set has 4 numbers.
Remainder: 1 → Number 8
Remainder: 2 → Number 4
Remainder: 3 → Number 1
Remainder: 0 → Number 6
990 ÷ 4 = 247 r 2
990th number = 4
(b)
Sum of each set
= 8 + 4 + 1 + 6
= 19
Number of sets
= 123 ÷ 4
= 30 r 3
Sum of the first 3 numbers
= 8 + 4 + 1
= 13
Sum of the first 123 numbers
= (30 x 19) + 13
= 570 + 13
= 583
Answer(s): (a) 4; (b) 583