The amount of blood in a person's body varies directly with body weight. A person who weighs 160 lb has about 4.6 qt of blood. About how many quarts of blood are in the body of a 175-lb person?

-How can you find the constant of variation?

-Can you write an equation that relates quarts of blood to weight?

-How can you use the equation to determine solution?

The statements expresses as

w ∝ b

where w = body's weight, b = amount of blood

Changing it into a direct variation becomes

w = kb or k = w/b

where k = proportionality constant

We know that k is obviously constant, we equation it into two states as

w ₁/b₁ = w₂/b₂

Given that w₁ = 160 lb, b₁ = 4.6 qt, b₂ = 175, w₂ = 175 lb. Then b₂ will be

160/4.6 = 175/b₂

b₂ = 160 / (4.6*175) = 160/805 = 0.20 quarts

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