79.in a meeting of 3 representatives from each of 6 different companies, each person shook hands with every person not from his or her own company . if the representatives did not shake hands with people from their own company, how many handshakes take place?
ans:135

80.from a group of 3 boys and 3 girls, 4 children are to be randomly¹ selected. what is the probability² that equal numbers of boys and girls will be selected?
ans: 3/5

81.the first roll of a cinema has 16 seats, the roll immediately after the first roll has 2 more seats than the first roll. every roll has two more seats than the roll immediately in front of it. the last roll of has 64 seats. how many seats does this cinema have?
ans: 1000

82.in the parallelogram shown, pq=4, qr=6,angleqps is 30 degree, what is the area of pqrs?


q ______________r
/l /
/ l /
p /__ l__________/s


83.a scientist recorded the number of eggs in each of the 10 birds' nests, what was the standard devition of the numbers of eggs in the 10 nests?
(1) the averge (arithmetic mean) number of eggs for the 10 nests was 4
(2) each of the 10 nests contained the same number
ans: b

84.the base of a retangular solid tank is a square, the length of each side of the square is 4 meters, the altitude of the tank is 6, if there is 16 cube meters water in the tank, what is the rate of the volume of water in the tank to the volume of the retangular solid tank?
ans: 1/6

85. is n more than m?
a. n is more than 2m-1 b. m is more than 1

86. ask what is the unit digit³ of n?
a. n is divided by 5, reminant is 3
b. n divided by 4, no reminant

87.some money deposit⁴ to bank, ask for the simple interest rate
a. each $70 , get $2.10 interest.
b. each $20 , get $0.66 interest

88.$20.000 deposit into bank, compand quarterly⁵, ask for this compand interest.
a.the intrest in 2nd quarter is 1.1 times more than the first quarter.
b. the intrest in 2nd quarter is 2 dollars more than the first quarter.

89. s=0.abc. ask s is more than 2/3?(old jj)
a.a+b is more than 14
b. a+c is more than 15

90. six musicians put into order, 3 of them have to be put together(their order does not matter), ask how many ways?

91.a1=3, a2=5, a(n+1)=an-a(n-1), ask s100=?(old jj)

92.buy wines, first 5 bottle $8each bottle, from 6 to 10(inclusive) $7each, more than 10 is $12 each. buy seperate $32 and $61, ask if buy together how much need to pay.(old jj)

93. 1/(9- 4xsqurt5) old jj