How do you evaluate #-2.9\times -13.7#?

1 Answer
Tony B
Dec 11, 2016

#color(blue)("Using a calculator")#

#(-2.9)xx(-13.7)=39.73#

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#color(blue)("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: #2.9xx13.7#
.......................................................................................................................
#color(green)("If the decimal is giving you problems do it this way.")#

#2.9" is the same as "29xx1/10#
#13.7" is the same as "137xx1/10#

Putting them together gives:#" "29xx137xx1/10xx1/10" "=29xx137xx1/100#

Leave the #xx1/100# until the very end.

#color(white)(.)#

#" "color(red)("The actual calculation")#
#color(white)(.)#

#20xx137" "->" "2740#
#color(white)(2)9xx137" "->ul(" "1233) larr" add"#
#" "color(white)(.)3973#

Now we use the #1/100#

#color(blue)(3973xx1/100 = 39.73)#

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