PSLE The first 15 numbers of a number pattern are given.
1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, 5, 1, 3, 7, ...
- What is the 159th number?
- What is the sum of the first 113 numbers?
(a)
Each set of numbers: 1, 3, 7, 5
Each set has 4 numbers.
Remainder: 1 → Number 1
Remainder: 2 → Number 3
Remainder: 3 → Number 7
Remainder: 0 → Number 5
159 ÷ 4 = 39 r 3
159th number = 7
(b)
Sum of each set
= 1 + 3 + 7 + 5
= 16
Number of sets
= 113 ÷ 4
= 28 r 1
First 1 number = 1
Sum of the first 113 numbers
= (28 x 16) + 1
= 448 + 1
= 449
Answer(s): (a) 7; (b) 449