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Answer:
4/5×3.75 = 3
Step-by-step explanation:
There are many solution strategies available. Among them are ...
- use a calculator to find 4/5×3.75 = 3
- convert the numbers to decimal and multiply by hand 0.8×3.75 = 3.000
- compute 2(2×3.75)/5 = 2(7.5)/5 = 15/5 = 3 in your head
- convert 3.75 to an improper fraction and multiply (4/5)(15/4)=15/5=3
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Additional comment
The mental arithmetic involved in adding a number to itself (doubling a number) is usually pretty easy. This means it is relatively easy to multiply by powers of 2, such as 4, 8, or 16. The second strategy listed above can be done in your head as ...
8/10×3.75 = 2×(2×(2×3.75))/10 = 2×(2×7.5)/10 = 2×15/10 = 30/10 = 3
The same product can be found as ...
8/10×3.75 = 8×(3.75/10) = 8×0.375 = 8×(3/8) = 3
In all cases, it is helpful to know your times tables, decimal equivalents of common fractions, and a few shortcut strategies for mental arithmetic. These are not difficult, but they do require you put some effort into memorizing them.
