Question #b3ab8

2 Answers
Sep 22, 2017

#~~$896.4#

Explanation:

Let the number be #x#
#$645.40=72%xx x#
#72%xx x=$645.40#
#1%xx x=$645.40-:72#
#~~$8.963888...#

#100%xx x=$8.963888...xx100#
#=896.3888...#
#~~896.4#

Sep 22, 2017

# x = $896 7/18# as an exact value

#x=$896.39# as an approximate value

Explanation:

The sign or symbol of % is like a unit of measurement but one that is worth #1/100#

So #1/100# and % are interchangeable.

The word 'of' is a bit like counting. 2 of apples #->2xx"apples"#
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Let the unknown value of dollars be #x#

So #72%" of "x# is the same as #72%xx x#

Then we have #72/100xx x =$645.40#

Multiply both sides by #100/72# (turns the #72/100# on the left into 1)

#72/100xx100/72xx x =100/72xx$645.40#

#72/72xx100/100xx x =100/72xx$645.40#

#1xx1xx x = $896 7/18# as an exact value

#x=$896.39# as an approximate value