Which of the following numbers is divisible by 33 ?

A1333

B2145

C2133

D1375

Answer:

To find the number divisible by 33, it must be divisible by both 3 and 11 ( $3 \times 11 = 33$ ).

## 1. Test for 3 (Sum of digits must divide by 3)

* 1333 $\rightarrow 1+3+3+3 = 10$

* 1375 $\rightarrow 1+3+7+5 = 16$

* 2133 $\rightarrow 2+1+3+3 = 9$ (Divisible by 3)

* 2145 $\rightarrow 2+1+4+5 = 12$ (Divisible by 3)

## 2. Test remaining numbers for 11

Check 2145 by subtracting alternating digits:

$(2 + 4) - (1 + 5) = 6 - 6 = \mathbf{0}$ Since the result is 0, it is divisible by 11.

Answer: 2145 is the correct option.

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