In: Computer Science
1+1 = 2 (In Decimal Number System)
Proof: In any a + b term,
'a' & 'b' are operands,
'+' is an addition operator, which sums up operands.
this is an addition/summation operation/process.
so, whenever b is added to a, that means a is increased by b. (vice-versa also true)
Let's understand this by the help of number line,

In a+b,
initially a & b both hold some number & they remain at those points in the number line (see diagram),
after a+b operation, a is increased by whatever the value b holds.
Now, in 1+1
operation a holds 1 & b holds 1, i.e., both a & b are situated in 1 point of the number line,
so, 1+1 operation implies, 1 is increased by 1, i.e., 1 is increased by 1 step towards the right side in the number line,
thus, the resultant value of 1+1 now points to 2.
So, the value contained by 1+1 is 2.
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NOTE: 1+1 = 2 (in Decimal Number System)
1+1 = 10(in Binary Number System)
In binary number system we represent numbers in 0 and 1 only.