Choose four numbers from 1, 2, 4, 8 and 16 to form a proportion. How many can be grouped

Choose four numbers from 1, 2, 4, 8 and 16 to form a proportion. How many can be grouped

8 2:1 = 8:4 4:2 = 16:8 2:1 = 16:8 1:2 = 4:8 2:4 = 8:16 1:2 = 8:16
1:8=2:16 8:1=16:2

4. Among the five numbers of 6, 9, 15 and 10, they can form () proportions
4. Among the five numbers of 6, 9, 15 and 10, they can form () proportions

It can make up 8 proportions

1. Use 0,1,2 The 10 digits, 9, make up five two digit numbers. Each digit is used only once. The sum of these 10 digits is required to be an odd number and as large as possible. What is the sum of these five two digit numbers?
2. There is a red, yellow, blue and white card with a number written on each card. Xiao Ming places the four cards as shown in Figure 7-1 to make them form a four digit number, and calculates the difference between the four digit number and its sum by 10 times. As a result, Xiao Ming finds that no matter what the number is on the white card, the calculation result is 1998. Q: what are the numbers on the red, yellow and blue cards?
Red yellow white blue
(Figure 7-1)

1: the sum of five two digit numbers must be as large as possible, so that each number must be as large as possible. Therefore, their ten digit numbers are 9, 8, 7, 6 and 5 respectively, and their ten digit numbers are 0, 1, 2, 3 and 4 respectively
（9+8+7+6+4）×10+（1+2+3+5）=351
2. According to the title, the title can be written as 1000 Red + 100 Yellow + 10 white + blue - 10 red - 10 yellow - 10 white - 10 blue
Equal to 990 Red + 90 yellow-9 blue = 1998 divided by 9 equals 110 Red + 10 yellow-blue = 222
That is, 100 red + 10 (red + yellow) - blue = 222
If red is 2, then 10 yellow blue = 2,
∵ blue represents a single digit, and the sum of 2 is a multiple of 10
The blue is 8 and the yellow is 1
The red, yellow and blue cards are 2, 1 and 8, respectively