5 th grade math - decimal multiplication using models

Apr 2015
15
0
New Jersey
Hi,
This might seem a silly question to you all Math experts.

I am having problem understanding the logic here. I understood the process of multiplying decimals using grid.
Here's the question:

The distance from Charlene's house to her school is 0.8 miles. Charlene rides her bike 7 tenth of the distance and walks the rest of the way. How far does Charlene ride her bike to school?

Underneath the question it says 0.7 x 0.8 =
They model the two decimals and multiplied.

My question is - isn't the answer given in the question? 7 tenth = 0.7 is the distance she rode her bike. I do not get the logic. Help :confused::confused:

Thanks,
wanttolearn
 

ChipB

MHF Helper
Jun 2014
312
130
NJ
She rode "seven tenths of the distance" and they want to know how many miles that is. Hence 7/10 of 0.8 miles is the answer, or 0.7 x .8 = 0.56 miles.
 
Apr 2015
263
57
Somerset, England
Let us look at this a different way that may help.

The whole distance is 0.8 miles.

Divide this up into tenths - ten of them, all equal.

So each tenth of the distance is 0.8 miles divided by ten = 0.8/10 = 0.08 miles

Charlene rides seven of these tenths or 7 times 0.08 = 0.56 miles

That leaves three tenths to walk or 3 times 0.08 = 0.24miles

As a check to convince ourselves we are right we can add the distance ridden(0.56miles) to the distance walked (0.24miles)

and we find the total distance

Indeed 0.56 + 0.24 = 0.8

The clue is always in the word of which I have made bold above.
The use of the expression 5 of them always means multiply.

Does this help?
 
Last edited:
Apr 2015
15
0
New Jersey
Thank you ChipB and studio. Excellent explanation.