When adding and subtracting, units MUST match
24in + 87in
= 111 in
24in + 87kg
*Can't combine because inches and kilograms are different units*
When multiplying, combine the units. In other words, the units are "summed".
9cm x 2cm
= 18 cm2
When dividing, follow the rule "stay, change, flip".
*Don't forget to also flip the units*
Use these images for a short review of fractions