First Solution
Do it with the fastest way by using formula
let (x + y(x) = z)
Using the formula above we will get the following answer
Substitute x = 1, y = 4, z = answer, into the equation x + y(x) = z
1 + 4(1) = 5
Substitute x = 2, y = 5, z = answer, into the equation x + y(x) = z
2 + 5(2) = 12
Substitute x = 3, y = 6, z = answer, into the equation x + y(x) = z
3 + 6(3) = 21
Let’s proceed to the question (8 + 11 = ?)
Given x = 8, y = 11, z = ?
8 + 11(8) = z
8 + 88 = z
96 = z

Secondly by using pattern.
1 + 4 = 5
2 + 5 = 12
3 + 6 = 21
4 + 7 = ??
5 + 8 = ??
6 + 9 = ??
7 + 10= ??
8 + 11= 96
Sequence |
Pattern |
Answer |
1 + 4 = 5 |
5 |
5 |
2 + 5 = 12 |
previous answer + 7 |
5 + 7 = 12 |
3 + 6 = 21 |
previous answer + 9 |
12 + 9 = 21 |
4 + 7 = 32 |
previous answer + 11 |
21 + 11 = 32 |
5 + 8 = 45 |
previous answer + 13 |
32 + 13 = 45 |
6 + 9 = 60 |
previous answer + 15 |
45 + 15 = 60 |
7 + 10= 77 |
previous answer + 17 |
60 + 17 = 77 |
8 + 11= 96 |
previous answer + 19 |
77 + 19 = 96 |
However, if you did manage to work out a solution for the sum yourself, there’s a tendency you came to the answer 40 instead. Here’s how you come to that answer:
1 + 4 = 5
2 + 5 + 5 = 12
3 + 6 + 12 = 21
8 + 11 + 21 = 40
But you did not sum up some other sequence like 4+7, 5+8, 6+9,7+10, you are jumping to conclusions directly which is 8+11+21 = 40, if you include that sequence you will also come out 96 answer.
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