Question

human heart in exercises 9–12, use the information. (see examples 3 and 4.)

1. how much does a heart weigh in pounds?
2. a human brain weighs about 3 pounds. how many ounces heavier is a brain than a heart?
3. how many quarts of blood does a heart pump in 1 minute?
4. how many gallons of blood does a heart pump in 1 day?

a human heart weighs about 10 ounces. on average, it beats about 70 times per minute and pumps about 2.5 fluid ounces of blood with each beat.

Explanation:

Problem 9: How much does a heart weigh in pounds?

Step1: Recall the conversion factor

We know that 1 pound = 16 ounces. The heart weighs about 10 ounces.

Step2: Convert ounces to pounds

To convert ounces to pounds, we divide the number of ounces by 16. So we calculate $\frac{10}{16}$.

Step3: Simplify the fraction

Simplify $\frac{10}{16}$ by dividing both the numerator and the denominator by 2, we get $\frac{5}{8} = 0.625$.

Step1: Convert brain weight to ounces

We know that 1 pound = 16 ounces. So for a 3 - pound brain, we calculate $3\times16 = 48$ ounces.

Step2: Find the weight of the heart in ounces

The heart weighs 10 ounces.

Step3: Calculate the difference

Subtract the weight of the heart from the weight of the brain: $48 - 10=38$ ounces.

Step1: Find the amount of blood pumped in a minute

The heart beats 70 times per minute and pumps 2.5 fluid ounces per beat. So the total amount of blood pumped in a minute is $70\times2.5 = 175$ fluid ounces.

Step2: Recall the conversion factor for quarts and fluid ounces

We know that 1 quart = 32 fluid ounces.

Step3: Convert fluid ounces to quarts

To convert fluid ounces to quarts, we divide the number of fluid ounces by 32. So we calculate $\frac{175}{32}=5.46875$ quarts.

Answer:

A human heart weighs $\boldsymbol{0.625}$ pounds (or $\boldsymbol{\frac{5}{8}}$ pounds).

Problem 10: A human brain weighs about 3 pounds. How many ounces heavier is a brain than a heart?