1. Which of these is the largest number?
A $2+0+1+3$
B $2 \times 0+1+3$
C $2+0 \times 1+3$
D $2+0+1 \times 3$
E $2 \times 0 \times 1 \times 3$
Solution
A We calculate the value of each of the given options in turn.
(a) $2+0+1+3=6$
(b) $2 \times 0+1+3=0+1+3=4$
(c) $2+0 \times 1+3=2+0+3=5$
(d) $2+0+1 \times 3=2+0+3=5$
(e) $2 \times 0 \times 1 \times 3=0$
So option A gives the largest number.

Remarks
You may have obtained the wrong answer if you interpreted $2+0+1 \times 3$ to mean $((2+0)+1) \times 3$ rather than $2+0+(1 \times 3)$. It is a standard convention (sometimes known as BIDMAS or BODMAS) that in evaluating an expression such as $2+0+1 \times 3$, the multiplications are carried out before the additions. We do not just carry out the operations from left to right. So in calculating $2+0+1 \times 3$, the multiplication $1 \times 3$ is done before the additions.
A decent calculator will produce the correct answer 5 if you press the keys
$2+0+1 \times 3=$
in this order. If your calculator produces a different answer, you should replace it!