# Homework Help: Weight Chart finding average

1. Jan 14, 2012

### lalahelp

1. The problem statement, all variables and given/known data

The weight of a baby measured over an 11-month period is given in the weight chart below for this problem.
Weight (lb) Age (months)
6.6 0 (birth)
7.4 1.0
9.6 2.0
11.2 3.0
12.0 4.0
13.6 5.0
13.8 6.0
14.8 7.0
15.0 8.0
16.6 9.0
17.5 10.0
18.4 11.0

(a) What was the average monthly weight gain for this baby over the period from birth to 3 months?
------- lb/month

(b) What was the average monthly weight gain for the baby over the period from 8 months to 11 months?
--------lb/month

(c) If a baby continued to grow at the same rate as in the first 3 months of life, what would the child weigh at age 12 years?

For part A I added the weights and divided by 3 but I got the wrong answer..... so how do I do it?

Im not sure how to solve parts B and C

2. Jan 15, 2012

### cepheid

Staff Emeritus
You should read the question more carefully. What you have computed is the average weight. What the question is asking for is the average weight GAIN over the course of a month.

Part b is the same as part A, only the average is being taken over a different time interval.

For part C, think about how you'd compute the total growth, if you've been given a growth RATE.

3. Jan 15, 2012

### lalahelp

So for part A I should subtract 7.4-6.6
9.6-7.4
11.2 -9.6

add the totals together and divide by three?

4. Jan 15, 2012

### lalahelp

Ok thanks I got A and B.
For part C Im not sure, Do I divide 1.53 (from part A) by 12?

5. Jan 15, 2012

### cepheid

Staff Emeritus
Yeah

You have a RATE of weight gain in pounds/month from part A. Let's say for example, the growth rate is 3 lbs and the starting weight is 5 lbs. If the growth rate remains constant, how much will the baby weight after one month? After two months? Now, how did you compute that? Hint: look at the units? what do you have to multiply a rate in pounds/month by in order to get the total weight gain, which is in pounds?

6. Jan 16, 2012

### lalahelp

Im not really understanding what your trying to explain.
so the rate of weight is not used?

7. Jan 16, 2012

### cepheid

Staff Emeritus