Use the multiplication facts 15 times 15 = 225 2 times 15 = 30 to help you menta

Question

Use the multiplication facts 15 times 15 = 225 2 times 15 = 30 to help you mentally calculate 17 times 15 Explain how your calculation method is related to the array below, which consists of 17 rows of dots with 15 dots in each row. Also write equations showing how your mental strategy for calculating 17 times 15 involves the distributive property. Write an equation that uses subtraction and the distributive property and that goes along with the following array: Mentally calculate 20 times 15, and use your answer to mentally calculate 19 times 15. Write an equation that uses subtraction and the distributive property and that goes along with your strategy. Without drawing all the detail, draw a rough picture of an array that illustrates this calculation strategy.

Explanation / Answer

1) 15 * 15 = 225

2 * 15 = 30

We have to find:

17 * 15 = ?

We can write,

17 = 2 + 15

So, ( 2 + 15) * 15 = ?...........Distributive property.

Here, 15 is distributed to 2 and 15

2*15 + 15 * 15 = 30 + 225 = 255

Number of rows * number of element per row gives us the answer.

So, 17 * 15 = 255 dots

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