How do you solve (- 4) + ( - 4) + ( - 4) + ( - 4) + ( - 4)?

3 Answers
Sep 18, 2016

#-20#

Explanation:

Adding a negative number is the equivalent of #color(blue)"subtraction"#

Hence #+(-4)=-4larr" subtract 4"#

The problem with this type of calculation is that the - sign denotes both negative numbers and subtraction.

The first term in the above sum is (- 4) which represents negative 4 while the other terms

#+(-4)" represent subtract 4"#

Rewriting the above sum to get.

#-4-4-4-4-4=-20#

Sep 18, 2016

Multiplication is the short cut for repeated addition.
#5xx(-4) = -20#

Explanation:

Multiplication is the short cut for repeated addition.

Instead of #3+3+3+3+3+3+3+3#, we can write the same thing as

#8xx3#

The sum of #3+3+3+3+3+3+3+3# is 24

The product of #8xx3 = 24" "larr# shorter to write, quicker to do!

In the same way #(-4)+(-4)+(-4)+(-4)+(-4)#

can be written as #5 xx (-4)#

=#-20" "larr# positive x negative = negative.

Sep 19, 2016

#-20#

Explanation:

One way of thinking about add and subtract is

Add is 'put with'
Subtract is 'remove from'

So in this question we have put together a lot of remove from's

This 'boils down to nothing but 'remove from'

So we have:

5 lots of remove 4

Thus: #-(5xx4) = -(20) = -20#