Question:medium
If the mean of the numbers $a, b, 8, 5, 10$ is $6$ and their variance is $6.8$, then $ab$ is equal to:
If the mean of the numbers $a, b, 8, 5, 10$ is $6$ and their variance is $6.8$, then $ab$ is equal to:
Show Hint
When given both mean and variance for two unknown variables, always solve for $(a+b)$ and $(a^2+b^2)$ separately. The identity $(a+b)^2 = a^2 + b^2 + 2ab$ will then directly yield the product $ab$.
Updated On: May 2, 2026
- $6$
- $7$
- $12$
- $14$
- $25$
Show Solution
The Correct Option is C
Solution and Explanation
Was this answer helpful?
0
Top Questions on Variance and Standard Deviation
- The mean of 5 observations is \(\frac {24}{5}\) and variance is \(\frac {194}{25}\) . If the mean of first four observations is \(\frac 72\) , then the variance of first four observations is
- JEE Main - 2024
- Mathematics
- Variance and Standard Deviation
- Let mean and variance of 6 observations a, b, 68, 44, 40, 60 be 55 and 194. If a > b then find a + 3b
- JEE Main - 2024
- Mathematics
- Variance and Standard Deviation
- Given data \(60, 60, 44, 58, 68, α, β, 56\) has mean \(58\), variance = \(66.2\), then find \(α^2 + β^2\).
- JEE Main - 2024
- Mathematics
- Variance and Standard Deviation
- From a lot of 12 items containing 3 defectives, a sample of 5 items is drawn at random. Let the random variable $X$ denote the number of defective items in the sample. Let items in the sample be drawn one by one without replacement. If the variance of $X$ is $\frac{m}{n}$, where $\gcd(m, n) = 1$, then $n - m$ is equal to ________.
- JEE Main - 2024
- Mathematics
- Variance and Standard Deviation
- Want to practice more? Try solving extra ecology questions todayView All Questions
