Question 393286: 60 - 20 = 20 + _______ what is the answer. I need to explain to my 8 year old.
Found 3 solutions by solver91311, ewatrrr, stanbon:
Answer by solver91311(24713)   (Show Source):
You can put this solution on YOUR website!
The first thing to explain is that the equals sign is like a balance scale. You can change the value any way you want on one side of the equals sign as long as you make the same value change on the other side to match it.
The trick is to manipulate things so that you have your blank line on one side and a single number on the other side so that the mathematical sentence reads, [blank] is equal to [some number] (or [some number] is equal to [blank] -- either way, it doesn't matter).
On the left side (I abbreviate LHS), you can do the indicated arithmetic. That doesn't change the value in the LHS, so you don't have to do anything to balance it in the RHS. 60 minus 20 = 40, so rewrite your equation:
So now you can see that the RHS has a 20 in it that we would like to eliminate, so add -20 to both sides (has to be both sides because if you reduce the value of the RHS by 20, you have to reduce the value of the LHS to keep the equation in balance):
\ =\ 20\ +\ (-20)\ +\ \underline{\text{ }})
Now just do the arithmetic. 40 plus a minus 20 is 20, and 20 plus a minus 20 is 0 leaving only the blank line in the RHS.
And that's your answer.
John
My calculator said it, I believe it, that settles it
Answer by ewatrrr(24785)  (Show Source):
You can put this solution on YOUR website!
Hi
Might recommend using a number line..back 20 from 60 for subtracting...
Going forward from 20(as in adding)to end up at that same '40' spot..
as the equal sign says...how far forward from 20 would that be??
Important concept! understanding the relationship between numbers
on the number line and how to move from one to another using
addition and subtraction. My best to You both.
Answer by stanbon(75887)  (Show Source):
You can put this solution on YOUR website! 60 - 20 = 20 + _______ what is the answer. I need to explain to my 8 year old.
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The answer is 20.
If I had to do this with an eight yr. old I would get a bunch of dimes.
I would make a group of 6 for the 60 (the left side of the equation)
and I would make a group of 2 for the 20 (the right side of the equation.
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I would form a "bank" of several dimes away from the two "groups".
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I would ask the 8 yr old to remove 20 from the left side and
put it in the bank.
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I would ask the 8 yr old to take enough from the bank so the group
on the right equaled the group on the left.
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If that did not answer the question you have posted, I would run
through the whole process again till the answer was seen.
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If you are looking for an algebric method go through the following.
60 - 20 = 20 + _______ what is the answer
Explain the the right side must balance the left side of the equal side
Evaluate the left side to get 40.
Ask what needs to be added to the right side so it will balance the 40
on the left.
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Good luck.
Cheers,
Stan H.
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