9) yes, he is correct.
50% as a decimal would be 0.50
7% as a decimal would be 0.07
10)Buy and Bye has a greater discount because 30% as a decimal is 0.30 and 1/4 as a decimal is 0.25.
0.30 is bigger than 0.25 so it is a bigger discount
Triangular sequence = n(n + 1)/2
If 630 is a triangular number, then:
n(n + 1)/2 = 630
Then n should be a positive whole number if 630 is a triangular number.
n(n + 1)/2 = 630
n(n + 1) = 2*630
n(n + 1) = 1260
n² + n = 1260
n² + n - 1260 = 0
By trial an error note that 1260 = 35 * 36
n² + n - 1260 = 0
Replace n with 36n - 35n
n² + 36n - 35n - 1260 = 0
n(n + 36) - 35(n + 36) = 0
(n + 36)(n - 35) = 0
n + 36 = 0 or n - 35 = 0
n = 0 - 36, or n = 0 + 35
n = -36, or 35
n can not be negative.
n = 35 is valid.
Since n is a positive whole number, that means 630 is a triangular number.
So the answer is True.
80.8, 40.4, 20.2, 10.1 (the numbers are going in half.)
1024, 512, 256, 128. (also going in half.)
