The average score of Xiaoming's previous tests was 84. This time, he had to take the test with 100 points to raise his average score to 86. What is the test this time? Don't use equations, have formulas, and give clear explanations Hurry!

It should be the eighth time
86-84 = 2 means that he has to add 2 points every time. 100-86 = 14 / 2 = 7 means that he has had seven tests before. This is the eighth time

The average score of Xiaohua's previous math tests was 80 points, and this time he got 100 points, which just raised the average score of these tests to 85 points?

A: This is the fourth time

At the beginning of school, the school bought 80 sets of desks and chairs. The unit price of each desk is three times that of each chair. The total cost is 9600 yuan. How much is each desk?

9600 ／ 80 × 3 ／ (3 + 1) = 90 (yuan)
So each table is 90 yuan

Haier appliances in the countryside activities, the original price of 1350 yuan is now 20% off, color TV is now cheaper than the original price of how many yuan?

270 yuan cheaper

Xiaoming's father bought a color TV, 205 yuan cheaper than before. (1) how much was the original price of this color TV
(2) How much did Xiao Ming's father spend on this color TV?

Original price = 205 (1-0.9) = 2050 yuan
Cost = 2050-205 = 1845 yuan
There are a few more questions

The original price of a color TV is 1800 yuan, but now it is 16 yuan lower than the original price. How much is the current price?

1800 × (1-16) = 1800 × 56, = 1500 yuan. A: the current price is 1500 yuan

The original price of a color TV is 1800 yuan, but now it is 16 yuan lower than the original price. How much is the current price?

1800 × (1-16) = 1800 × 56, = 1500 yuan. A: the current price is 1500 yuan

The current price of a color TV set is 1650 yuan, 12% lower than the original price. How much is the original price of each set?
The school bought 120 bottles of red ink, 1 / 4 more than the blue ink. How many bottles of blue ink?

The original price of TV set: 1650 (1-1 / 12) = 1800 yuan
The number of blue ink bottles: 120 (1 + 1 / 4) = 96

1. The current price of a TV set is 5600 yuan, 20% lower than the original price. How much is the original price?
2. The county greening team planted 120 trees on the first day and 136 trees on the second day. At this time, the ratio of the planted trees to the remaining trees is 4:9. How many trees are not planted
3. Build a cylindrical biogas digester. The diameter of the bottom is 4 meters and the depth is 3 meters. If cement is applied on the bottom and around the digester, how many square meters is the area of cement applied?
4. A pile of coal is cone-shaped, with a diameter of 3 meters at the bottom and a height of 2 meters. Each cubic meter of coal weighs about 1.5 tons. How many tons does this pile of coal weigh in total? (keep the integer)

5600 ± (1-20%) = 7000 yuan. Suppose there are x trees left (120 + 136): x = 4:9x = 576s = 3.14 * (4 / 2) * (4 / 2) + 3.14 * 4 * 3 = 50.24 cubic meters. The bottom radius is 3 / 2 = 1.5 meters. The volume of this pile of coal is 3.14 * 1.5 * 1.5 * 2 / 3 = 4.71 cubic meters. The total weight of this pile of coal is 4.71 * 1.5 = 7.065 tons = 7 tons

The price of a TV set is 5400 yuan, which is 600 yuan lower than the original price. How much is the price reduction?

600/(600+5400)=0.1
It's down 10%

The average score of Xiaoming's previous tests was 84. This time, he had to take the test with 100 points to raise his average score to 86. What is the test this time? Don't use equations, have formulas, and give clear explanations Hurry!