Word problem

A word problem:
Luisa has four times as much money as Mary. If Luisa has $240 more than Mary, how much money do they have in all?
Mary has less. Let Mary's money be represented by ONE BLOCK. Then, Luisa's money would be FOUR BLOCKS.

Now, the problem says the DIFFERENCE in their monies is $240. The difference is also three blocks.

So, three blocks is $240.
Then one block is $80.

The question was, how much money do they have in all? They have 5 x $80 = $400 together.

The same can be solved with algebra. Instead of blocks, we use x. Mary has x, Luisa has 4x. The difference 4x − x is $240. As an equation:

4x − x = $240
3x = $240
x = $80

Then, together they have 4x + x = 5x, which is 5 x $80 = $400.

You can use the exact same kind of reasoning and block model to solve any similar word problem where one thing is so many times as another, and the actual difference is also given. Try this on your own:

A daddy elephant weighs 7,000 pounds more than his child. Also, he weighs three times as much as his child. How much does the small elephant weigh?


Anonymous said…
World Problem:
small elephant weights 3,500 lbs.

request confirmation. thanks

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