In a group of ducks and buffaloes, the total number of legs are 24 more than twice the number of heads. Find the total number of buffaloes.

Answer: Option D

Explanation:

Let the boys are X, then girls are 7X, total = X+7X = 8X

So it should be multiple of 8, 30 is not a multiple of 8.

Answer: Option C

Explanation:

As per BODMAS rule, first we will solve the equation in bracket then we will go for division
= (9240)/28 = 330

Answer: Option A

Explanation:

By taking LCM we get
=\begin{aligned} \frac{28+14+7+4+2+1}{28}
= \frac{56}{28} = 2\end{aligned}

Answer: Option D

Explanation:

b-[b-(a+b)-{b-(b-a+b)}+2a]
=b-[b-a-b-{b-(2b-a)}+2a]
=b-[-a-{b-2b+a}+2a]
=b-[-a-{-b+a}+2a]
=b-[-a+b-a+2a]
=b-[-2a+b+2a]
=b-b
=0

Answer: Option B

Explanation:

= (31/10) * (3/10) + (7/5) / 20
= (3.1) * (.3) + (1.4) / 20
= 0.93 + 0.07
= 1