"If the circus were to sell all of its 220 tickets for this month's performance at its usual price, the revenue from sales would be 10% greater than that collected last month"
=> 220 tickets sold this month yield 10% greater revenue compared to the last month
=> As this is compared against the last month's value, base value is that of last month
=> Let us take the tickets sold last month as X. As a 10% increase results in 220 in this month, (220-X)/X = 10% = 10/100
=> on solving , X = 200
(or we can simply guess 200 as 10% of it 20 and 200+20 = 220)
"If the circus raised the ticket price by 5% and sold only 200 tickets as a result, what percent less would last month's revenue be compared to this month's revenue"
=> This time the comparison is based on this month's value
=> base value should be this month's
=> suppose last month's value is 100, this month's value must be 105, as there is 5% hike
=> To get the % of decrease in the last year in comparison with this year, go for a reverse calculation
=> (105-100) decrease from 105 => 5*100/105 % = 100/21 %
Ravi Sankar Vemuri