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# Addition and subtraction word problems: gorillas

Sal solves addition and subtraction word problems.

## Want to join the conversation?

• does this count as clearing a variable? something like pre algebra ?
• Yeah, this is like solving really simple equation.
• I have always had trouble with math and understanding but one question How would set up a problem for a subtracting. I have seen people set it up two ways for an example the one you did for 20- 5 ive seen it both ways and subtracted two ways with burrowing and not borrowing which way is the correct way?
• 20 - 5 does require borrowing. Whenever a number goes under 0, it always has to borrow from it's big brother. 0 - 5 goes under 0, so it has to borrow from it's big brother, the two. 2 - 1 = 1, and now the 0 becomes 10. 10 - 5 = 5 and 10 + 5 = 15! The answer is 15! I hope this helps!
• Question,

Why is the variable so important in math
• Variables are very (even extremely) important in math because they are placeholders for unknown values in an equation, function, etc. For example, if we have the equation 2x=6, we can solve for the variable (and find that x=3). But without variables there is no way to do that. We would have to directly solve for 6÷2. Though interpreting the calculation that way is not difficult, imagine if you have several different values performing different operations, requiring us to rewrite and rearrange the order of several things.

In functions, variables provide the same thing and convenience. For a function, such as y=2x, we can use it to help see what y will equal for particular x values (note that both y and x are variables). But without variables, we would have to solve each equation one by one:

• 2x1=2

• 2x2=4

• 2x3=6

• 2x4=8

• 2x5=10

• And so on in a pattern of 2 times the next value in a never-ending list

So variables provide a very big convenience in writing calculations, functions, tables, and other sorts of things.

[R]
• Why would the 1st task be written in a way that makes the end result inconclusive? As it is stated there we do not know whether all or only ''some'' of the 14 gorillas were actually lifting weights.
• When you get a question that is ambiguous you have to see how the problem should be worded to make a question that allows us to write equations. In this case the problem says "some"; now, can you use that to solve a problem?, I don't think so, it is ambiguous. If you use "all" instead, you can start solving it.
• no, I don't understand, my question was; Raj and Carlos are reading. Carlos read a chapter in 4 minutes, which is 3 minutes less time than it takes Raj.

- you can find who took less time and who took more time to read. Draw it on a piece of paper if it helps.

- You also know how long one of them took to read,

- You know the difference in reading time between the two.

With all that you should be able to find out how long the other one took to read.
• i'm not good at math i'm slow
• do not say that you should just trust in yourself OK
(1 vote)
• how do you now if it is addition or subtration
• This is hard for me i am a bart `crys`