Question

Prove '(2.2 + 4.7) + 3.8' is same as '2.2 + (4.7 + 3.8)'.

Answer 1

We know that, instead of adding two numbers one after another, we need to only add their sum.

i.e., $(x+y)+z=x+(y+z)$, for all numbers $x,y$ and $z$.

Since the above is true for all numbers $x,y$ and $z$, it must be true for $x=2.2,y=4.7$ and $z=3.8$.

So, (2.2 + 4.7) + 3.8 = 2.2 + (4.7 + 3.8)

Hence proved.