6897 is divisible by

Answer: Option D

Explanation:

Trick: Above equation can be solved by using following formula
$$\begin{aligned} (a^2 + b^2) = \frac{1}{2}((a+b)^2 + (a-b)^2) \end{aligned}$$

Answer: Option A

Answer: Option B

Explanation:

Trick: when multiplying with $$\begin{aligned} 5^n \end{aligned}$$ then put n zeros to the right of multiplicand and divide the number with $$\begin{aligned} 2^n \end{aligned}$$
So using this we can solve this question in much less
time.
$$\begin{aligned} 1939392 \times 5^4 = \frac {19393920000}{16} = 1212120000 \end{aligned}$$

Answer: Option D

Answer: Option B

Explanation:

(555 + 445) * 2 * 110 + 30 = 220000 + 30 = 220030