We need to simplify by using mental math 275 + 180 + 120=.
First we need to find numbers that can add easly.
We have 180 and 120 there. Adding those numbers are easy because both has 0's in ones place.
So, we could just add 18 and 12 and put a 0 in ones place.
18+12.
In oder to add 18+12 by mental math, we can write 18 as 20-2 and 12 as 10+2.
We can add 20 and 10 easily that gives 30.
But we remain -2 and +2 there. -2+2=0.
So, we could write it as
18+12 = (20-2) +(10+2) = 20+10 -2+2 = 30+0=30.
Therefore, 180+120 = 300.
Now, 275 + 180 + 120 = 275 +300.
We know 275= 200 + 75.
So, 275+300 could be written as 200+75 +300.
Adding 200+300, we get 500.
Now adding 500+75, we get 575.
In simple way, we could write the steps..
275 + 180 + 120 = 275 + 300 = 275+300 = 575.
