Can't remember sums

Zander490

New member
Joined
Mar 31, 2020
Messages
3
How do I keep track of numbers when solving two or more digit problems?

When I tired to solve 23 + 45 this morning, i realized that I had forgotten the sum I calculated for 3+5 after I solved 2+4. Also, when I tried to add 71 + 24 in my head, I got 59. I got the numbers backward somehow! Is there some technique to better my memory just enough to solve basic math? This is embarrassing.
 
Are you doing the calculations in your head?
I do something like this:
E.g. 23+45.
1. Take the first number and add tens of the second number: 23+40=63
2. Add ones of the second number: 63+5=68

You can add tens, ones, then get the total. But the above approach is easier, I think. In the first step you are adding just tens and keeping ones digit of the first number the same. In the second step you are adding ones keeping tens the same, except for the case when you are going over 10 - then just increase tens by 1.
 
This is embarrassing.
Addressing this comment: Don't worry about. I'm currently playing an idle game where I have to divide by 3 in my head a lot. You wouldn't believe how many times I've screwed that up. It happens to the best of us. Just keep going back through the problem to see what you've done wrong. Putting it down on paper helps you recall how to do it in your head.

-Dan
 
Are you doing the calculations in your head?
I do something like this:
E.g. 23+45.
1. Take the first number and add tens of the second number: 23+40=63
2. Add ones of the second number: 63+5=68

You can add tens, ones, then get the total. But the above approach is easier, I think. In the first step you are adding just tens and keeping ones digit of the first number the same. In the second step you are adding ones keeping tens the same, except for the case when you are going over 10 - then just increase tens by 1.

Yes, i'm doing the work in my head. I hadn't thought about adding from left to right, but what happens when you have to carry a ten?
 
Yes, always add from left to right unless the numbers have too many digits----you decide on what too many are.

What about carrying 10's--just do it. If I was adding
125
356
145

I would start with 3+1 is 4, 4+1 is 5 OR just realize that the left column adds up to 5 and say 500.
Then I would add 50--sum is 550. Then add 40--sum is 590. Then add 20--590-600-610---sum is 610.
Then I would jump on 5+5=10--so 610--620-----sum is 620.
Now add the last 6 and the sum is 626. Do the carry overs as they come up.
 
So, just go for it and add whatever remainder(?) that comes up to what I already have calculated on the left? I guess that makes sense. Thanks. But I might be back with other questions about basic math later.
 
Top