Compatible numbers with decimals are nearby or equivalent values that make addition, subtraction, multiplication, or division easier to perform mentally, such as replacing 3.98 and 2.03 with 4 and 2 to estimate a sum or recognizing that 7.2 ÷ 0.8 equals 72 ÷ 8. The selected numbers must preserve the operation’s scale and produce a sensible estimate or exact simplification, rather than being changed arbitrarily; advanced approximation methods with more general numbers are not included.
Compatible numbers are numbers that are close to the original numbers or equivalent to them, but make the operation easier.
For division, you can multiply both the dividend and divisor by the same power of . This keeps the quotient the same.
Example: Find .
The numbers and are compatible numbers because they make the division easy while keeping the value of the quotient unchanged. Always change both numbers in the same way so the operation stays equivalent.
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