If the mean of x₁, x₂ is 7.5, and the mean of x₁, x₂, x₃ is 8, then the value of x₃ is

1. 9

2. 8

3. 7.5

4. 6

If each observation of the data is increased by 5, then their mean

1. remains the same

2. becomes 5 times the original mean

3. is decreased by 5

4. is increased by 5

For drawing a frequency polygon of a continuous frequency distribution, we plot the points whose ordinates are the frequencies of the respective classes and abscissae are respectively :

1. upper limits of the classes

2. lower limits of the classes

3. class marks of the classes

4. upper limits of preceding classes

Median of the numbers 4, 4, 5, 7, 6, 7, 7, 3, 12 is

1. 4

2. 5

3. 6

4. 7