6. the recommended heart rate for weight management exercise and improming/
cardio fitness, in beats per minute, depends on a person's age and can be
represented by the expression 0.7(220 - a).
part a: what does the variable in the expression represent?
part b: rewrite the expression using the distributive property.
part c: what is the recommended heart rate for a 20-year-old person

Part A = Age, Part B = 154 - 0.7a, Part C = 140 beats per minute (BPM)

Step-by-step explanation: The question states "...in beats per minute, depends on a person's age and can be represented..." and the variable is a, so a is age. To rewrite an expression, you need to multiply the number outside the parentheses with the terms inside the parentheses. In this case 0.7 * 220, which is 154 and 0.7 * a which is 0.7a. So the expression rewritten is 154- 0.7a. In order to solve question C you need to plug in the variable. So 0.7(220 - 20) or 154 - 0.7 * 20, whichever is easier. After solving, your answer will be 140 beats per minute.

56.6

step-by-step explanation:

the ratio of the perimeters is equal to the scale.

the ratio of the areas is equal to the square of the scale.

34 / 20 = k

a / 19.6 = k²

substituting:

a / 19.6 = (34 / 20)²

a = 19.6 (34 / 20)²

a ≈ 56.6

-6 is the correct option from the above given options