fyw2025
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a boy is building a pyramid out of building blocks. he put 20 blocks in the first row, then he puts 19 blocks in the row above, and so on. find the total number of blocks he needs. find the total number of blocks he need

Respuesta :

sply0992

Answer:

210 blocks

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Step-by-step explanation:

sqdancefan

Answer:

  210

Step-by-step explanation:

The formula for the sum of numbers 1 to n is ...

  sum = (n/2)(n +1)

The sum of numbers 1 to 20 is ...

  sum = (20/2)(20 +1) = 10(21) = 210

The boy will need 210 blocks for his pyramid.

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Additional comment

The sequence of totals required for n rows is 1, 3, 6, 10, 15, 21, .... These are called "triangle numbers."

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