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If a - b = 3 and \begin{aligned} a^2 + b^2 = 29 \end{aligned}, then find the value of ab

  • 7
  • 8.5
  • 10
  • 12

Answer: Option C

Explanation:

Remember the formula, if not then cram it :)
\begin{aligned} 2ab = (a^2 + b^2)- (a-b)^2 \end{aligned}
=> 2ab = 29 - 9 = 20
=> ab = 10

Similar Questions :

1. (3080 + 6160) / 28

  • 380
  • 350
  • 330
  • 310

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

2. \begin{aligned}
(3\frac{1}{4}\div \{1\frac{1}{4} - \frac{1}{2}(2\frac{1}{2} - \overline {\frac{1}{4} - \frac{1}{6}} ) \} )
\end{aligned}

  • 78
  • 88
  • 98
  • 108

Answer: Option A

Explanation:

Tip:
As you can see, there is bar over
\begin{aligned}
\overline{\frac{1}{4}-\frac{1}{6}}
\end{aligned}
So their sign will be changed from - to + as
\begin{aligned}
\frac{1}{4}+\frac{1}{6}
\end{aligned}

3. Value of \begin{aligned} 2^5 \times 9^2 \end{aligned} has been written as 2596, what is the difference between actual value.

  • 1
  • 2
  • 3
  • 4

Answer: Option D

4. Company workers decided to raise Rs. 3 lakhs by equal contribution from each. Had they contributed Rs. 50 each extra, the contribution would have been Rs. 3.25 lakhs. How many workers were they?

  • 300
  • 400
  • 500
  • 600

Answer: Option C

Explanation:

N * 50 = (325000 - 300000) = 25000
N = 25000 / 50
= 500

5. a * b = 2a - 3b + ab, then 3*5 + 5*3 = ?

  • 20
  • 21
  • 22
  • 23

Answer: Option C

Explanation:

= 2(3)-3(5)+(3*5) + 2(5)-3(3)+(5*3)
= 6-15+15+10-9+15 = 31-9 = 22

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