A shop advertises 10% off its prices in a sale. A book is £6.30 in the sale
How much was it before the price reduction?

£7

Step-by-step explanation:

Since the sale is 10% the original price, every item is being sold for 90% of its original price. Now the problem is: £6.30 is 90% of what number?

Let x = original price before sale

6.30 = 0.9x

0.9x = 6.3

Divide both sides by 0.9

x = 6.3/0.9

x = 7

£7

step-by-step explanation:

85.560%

step-by-step explanation:

conditional probability is defined as:

p(a|b) = p(a∩b) / p(b)

in other words, the probability that a occurs, given that b has occurred = the probability that both a and b occur / the probability that b occurs.

in this example:

p(turns 64 | turns 44) = p(turns 64 & turns 44) / p(turns 44).

if someone turns 64, they must have already turned 44, so:

p(turns 64 | turns 44) = p(turns 64) / p(turns 44)

on page 42, we see that of the original 100,000, 94944 turn 44, and 81234 turn 64.   therefore:

p(turns 64 | turns 44) = 81234 / 94944

p(turns 64 | turns 44) = 0.85560