12. a rectangular sheet of cardboard measures 64 cm by 15 cm.
suppose the width is changed to 16 cm.
what would the length have to be for the rectangle
to have the same area?

Area of rectangle: length × height

Let the new length be x.

64 × 15 = 16 × x

x = ( 64 × 15 ) ÷ 16

x = 60cm

Why does this work?

It is stated that the area is the same. With that logic, you need to think "I know the area of the rectangular cardboard, so what number multiplied by 16 gives the same area?"

If you check the answer, you will find that 60 × 16 is also .

3

step-by-step explanation:

in standard form:

a= dictionaries

b= maps

you have to buy 3 dictionaries, so put a 3 next to the a (dictionaries) so that you can multiply them by each other.

a3+b= 60 (the amount of money you have)

we already know the cost of a=15 so replace a with $15

($15 x 3)+b=60

multiply 15 and 3 to get $45 and replace it with $45

45+b=60

and then replace b with 15 to get the total:

45+15=60

that means you have $15 left after buying 3 dictionaries.

15 divided by the cost of a map ($5) equals 3.

so you can buy 3 maps.

sorry if it was confusing!

step-by-step explanation:

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