What is the Average Monthly Weight Gain for a Baby Over a Specific Time Period?

[lalahelp]

Homework Statement

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


please help

 

[cepheid]

Homework Statement

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?

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.

 

[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?

 

[lalahelp]

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

 

[cepheid]

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?

Yeah

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

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?

 

[lalahelp]

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

 

[cepheid]

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

Just answer this question here:

Let's say for example, the growth rate is 3 lbs/month 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?

I'm sure you know how to answer that. Once you do, ask yourself, "how did I do that?" It's same as the method for part C.

It's the same method in general for whenever you're given a *rate of change* of some quantity with time, and you want to figure out the total change in that quantity over some time interval. Another example: say I'm moving along in my car at 50 km/h. After 3 hours, how far will I have moved? You find the answer in exactly the same way, only this time the quantity in question is distance rather than weight.

 

[lalahelp]

okkk now I understand what you mean thank you!