color(blue)("Using a calculator")Using a calculator
(-2.9)xx(-13.7)=39.73(−2.9)×(−13.7)=39.73
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color(blue)("None calculator method")None calculator method
When multiplying or dividing, if the signs are the same the answer is positive. If they are not the same then the answer is negative.
In this case they are both the same so the answer is positive
So the question gives the same answer as: 2.9xx13.72.9×13.7
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color(green)("If the decimal is giving you problems do it this way.")If the decimal is giving you problems do it this way.
2.9" is the same as "29xx1/102.9 is the same as 29×110
13.7" is the same as "137xx1/1013.7 is the same as 137×110
Putting them together gives:" "29xx137xx1/10xx1/10" "=29xx137xx1/100 29×137×110×110 =29×137×1100
Leave the xx1/100×1100 until the very end.
color(white)(.).
" "color(red)("The actual calculation") The actual calculation
color(white)(.).
20xx137" "->" "274020×137 → 2740
color(white)(2)9xx137" "->ul(" "1233) larr" add"
" "color(white)(.)3973
Now we use the 1/100
color(blue)(3973xx1/100 = 39.73)
