## Weight in Pounds

## Work Time

# Weight in Pounds

Many people in the United States know their weight only in pounds. There is a rule of thumb that can help you use your weight in pounds to estimate your weight in kilograms: divide your weight in pounds by 2, and then subtract 10% of that number from the result.

- Let
*p*= a person’s weight in pounds. Write an expression for the person’s weight in kilograms. - Can you write an equivalent expression for the person’s weight in kilograms?
- Use the rule of thumb to find the weight, in kilograms, of a person who weighs 115 lb.
- Use the rule of thumb to find the weight, in pounds, of a person who weighs 49.5 kg.

## Hint:

*Equivalent expressions*are expressions that have the same value when a given value is substituted for the variable. For example, 3(*x*+ 6) and 3*x*+ 18 are equivalent expressions. When*x*= 2, both expressions have the value 24.- If you have 80 pounds, how do you take 10% of it?
- How might you use the distributive property to write equivalent expressions?
- Now think back to the difference between an expression and an equation. To find a person’s weight in kilograms, do you need to evaluate an expression or solve an equation?
- To find a person’s weight in pounds, do you need to evaluate an expression or solve an equation?