A level maths help

[steel vector]

I thought the standard deviation would increase by x1.4 instead of dividing it by x1.4, and why is it the opposite for the -20 too?

[visual yacht]

since standard deviation is a measure of spread adding and subtracting doesn't change its value

[steel vector]

yes i undertsnad that

i meant the mean being -/+ 20

why do you add 20 to the mean

and divide them both by 1.4 instead of timesing them?

[visual yacht]

$\bar{y} = 1.4\bar{x} - 20 \implies \bar{x} = \frac{\bar{y} + 20}{1.4}$

[formal rivet]

clarence

[visual yacht]

where x bar and y bar are the means

since if you do any operation to the mean you have to do the inverse operation to get back to the original mean

[steel vector]

ok, but what in this question means you have to do the inverse operation though?

[visual yacht]

it says find the mean of x