(2) Because 1392 yuan divided by the highest fare 13 yuan is greater than 100 people, it can be determined that the total number of people exceeds 100 people;
It can be concluded that the total number of people is: 1080/9= 120.
Set up an x person and a b person; De: x = 120-y
13x+11y =1392 instead of x =120-y.
de: 13 *( 120-y)+ 1 1y = 1392。
13 * 120- 13Y+ 1 1Y = 1392
13 * 120- 1392 = 2Y
Y=84 people
A: There are 36 people in Group A and 84 people in Group B;
If the store needs to buy X ties, it should buy them according to the first scheme, and the payable amount is 200×20+(x-20)×40=40x+3 200 (Yuan).
If purchased according to Scheme II, the payable amount is (200×20+40x)×90%=36x+3 600 (RMB).
Let y = (40x+3 200)-(36x+3600) =4x-400 (yuan).
(1) When y
(2) When y =0, 4x-400=0, that is, x = 100, so scheme 1 saves money as scheme 2;
(3) when y > 0, 4x-400 >: 0, that is, x > 100, and scheme 2 saves money than scheme 1.
To sum up, when buying more than 20 ties but less than 100, choose option 1 to save money; When buying a tie is equal to 100, choosing two schemes will also save money; Buy ties above 100 and choose the second option to save money.