Marie works for an optician. She records the depth of a lens in each of the 100 pairs of glasses on display.
Depth
Her results are summarised in the table.
Number of pairs of glasses
Depth of lens, x mm,
to the nearest mm
10 << 20
5
20 < X < 30
20
30 < x < 40
23
40 <r< 50
52
In which group does the median lie?
(1 mark)
10 < x < 20
20 < x < 30
30 < x < 40
40 < x < 50​

The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends more than a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?