Mr. Zhang has two stamps of 50 and 80. He can pay with them______ How much do you need to pay to send a letter

Mr. Zhang has two stamps of 50 and 80. He can pay with them______ How much do you need to pay to send a letter

Because the stamps with 50 points and 80 points each can be combined into six different postage rates: 50 + 50 = 100 (points), 80 + 80 = 160 (points), 50 + 80 = 130 (points), 50 + 50 + 80 = 180 (points), 50 + 80 + 80 = 210 (points), 50 + 50 + 80 + 80 = 260 (points), plus the two denominations of 50 points and 80 points, a total of 6 + 2 = 8 different postage rates can be paid

Li Ming has two 70 Fen stamps and two 80 Fen stamps. How many kinds of postage can he pay with these stamps? How much for each?

Can you stop calling Li Ming
seventy
70+70
70+80
70+70+80
70+70+80+80
eighty
80+80
80+80+70
It's like this

The number of stamps collected by Xiaoming is 1.5 times that of Xiaogang. After Xiaoming gave Xiaogang 25 stamps, they were equal. How many stamps did each of them have

"If Xiaogang has * stamps, Xiaoming has 1.5 *
1.5*-25=*
1.5*-*=25
0.5*=25
*=50
1.5*50=75

Xiao Ming and Xiao Gang are good friends. They both like collecting stamps. Xiao Ming finds that two fifths of his stamps are exactly 80,
He is going to exchange 3 / 10 of the stamps with Xiao Gang. How many stamps is Xiao Ming going to exchange? It takes Master Wang four hours and master Li six hours to process a batch of parts. If they work together, how many hours can they complete the task?

Two fifths of the stamps is exactly 80. Divide 80 by two fifths to calculate the total number of stamps 200. Multiply 200 by three fifths to calculate the exchange of 60 stamps. Master Wang takes 4 hours to calculate 1 / 4 of Master Wang's work per hour. Master Li takes 6 hours to calculate 11 / 6 of Master Li's work per hour

In known arithmetic sequence {an}, 1, A1 = 3 / 2, d = - 1 / 2, Sn = - 15, find n

The first n terms and formulas
Sn=na1+n(n-1)d/2
-15=n×3/2+n(n-1)×(-1/2)÷2
n²-7n-60=0
(n+5)(n-12)=0
N = - 5 (rounding off) or n = 12
To sum up, n = 12

In the arithmetic sequence {an}, A1 = 4, and A1, A5, A13 are equal ratio sequence, then the general term formula of {an} is ()
A. An = 3N + 1b. An = n + 3C. An = 3N + 1 or an = 4D. An = n + 3 or an = 4

According to the meaning of the title, a 52 = a 1 · a 13 ∵ a 1 = 4, ∵ (4 + 4D) 2 = 4 (4 + 12D), D 2 = D ∵ d = 0 or D = 1, when d = 0, an = 4, when d = 1, an = 4 + n-1 = n + 3