Number Patterns
The numbers in the sequence below follow a certain pattern:
3, 7, 13, 21, ___, 43
What number should go in the blank?
Word Problem
A bridge is built across a river. One quarter of the bridge is over the left bank of the river and one third of the bridge is over the right bank. The river is 120 m wide. How long is the bridge?
Let’s look at the differences between each term:
ReplyDelete7 − 3 = 4
13 − 7 = 6
21 − 13 = 8
The differences are increasing by 2:
4, 6, 8...
So the next difference should be:
8 + 2 = 10
Add 10 to the last number:
21 + 10 = 31
Now check:
31 + 12 = 43
(Next difference is 12, continuing the pattern: 4, 6, 8, 10, 12...)
Final Answer: 31