Multiplying by 715
To multiply a multiple of 7 by 715, perform the following:
• Divide the number by 7.
• Multiply the number by 5.
• Write the result on the right, using three digits. Then
write the result on the left.
Example:
28 × 715 =
Solution:
• 28 ÷ 7 = 4
• 4 × 5 = 20
• Write 020 as 20 is the result and you must use
three-digits. Then write the 20 on the left. The final answer is
20020.
Answer:
28 × 715 = 20020.
Example:
84 × 715 =
Solution:
• 84 ÷ 7 = 12
• 12 × 5 = 60
• Write 060 on the right (using three digits). Then write
60 on the left. The final answer is 60060.
Answer:
84 × 715 = 60060.
Note: This trick works because  .
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