BrainDen.com - Brain Teasers

## Question

How much does the baby weigh if the mother weighs 100 pounds more than the combined weight of the baby and the dog, and the dog weighs 60 percent less than the baby? ## Recommended Posts

• 0

25 lbs

##### Share on other sites
• 0

25 lbs

Basic system of equations with 3 variables...from the statements:

Let b = baby's weight, d = dog's weight, w = woman's weight...

if the mother weighs 100 pounds more than the combined weight of the baby and the dog

EQUATION 1: b + d + 100 = w

the dog weighs 60 percent less than the baby

EQUATION 2: d = 0.4*b

and then from the picture, we know

EQUATION 3: b + d + w = 170

Then just solve the system

Substitute equation 2 into equations 1 and 3:

1) b + 0.4b + 100 = w and 3) b + 0.4b + w = 170

1) 1.4b + 100 = w and 3) 1.4b + w = 170

Then substitute equation 1 into equation 3:

1.4b + 1.4b + 100 = 170

Solve for b:

2.8b = 70

b = 25

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account. ×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×