Question

Delip measured the speeds, x km per hour, of 70 cars on a road where the speed limit is 60 km per hour.
His results are summarised by Σ(x − 60) = 245.
His friend Sachim used values of (x − 50) to calculate the mean.
(ii) Find Σ(x−50).

Answer 1

@phi

Answer 2

mean = 245/70+60

mean = y/70 + 50

y = 245+700 ... though no so sure

Answer 3

70 cars,
Σ(x − 60) = 245
Σx - 60*70=245
Σx = 245+60*70
Σx/70 = x_mean = 60+3.5= 63.5

(x − 50) to calculate the mean. I assume he found the mean of x-50

(Σ(x-50))/70 = Σx/70 - 50*70/70 = x_mean-50
(Σ(x-50))/70 = 63.5-50 = 13.5
Σ(x-50)= 70*13.5
Σ(x-50)= 945

Answer 4

It does match experimentX's result

Answer 5

usually my hunch is right ... thanks for confirming