Elgo is building pyramid-like shapes using small cubes as shown below. How many cubes will he use to make pyramid 5
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Given:
The four pyramid-like shapes built by Elgo.
To Find:
The no of cubes required to make the fifth pyramid.
Calculation:
The no of cubes in 1st pyramid = 1 = 1²
The no of cubes in 2nd pyramid = 5 = 1² + 2²
The no of cubes in 3rd pyramid = 14 = 1² + 2² + 3²
The no of cubes in 4th pyramid = 30 = 1² + 2² + 3² + 4²
Looking at the above pattern, the no of cubes required to built the fifth pyramid = 1² + 2² + 3² + 4² + 5²
⇒ n = 55
- So a total of FIFTY FIVE (55) cubes will be required by Elgo to make the fifth pyramid.
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