In Grade 5 Class 2, there are 3 students aged 13, 15 students aged 12, 11 students aged 11, and 21 students aged 10. What is the average age of the class?

The average of the three numbers A, B, C is 10. The average of the four numbers A, B, C, D is 11. Find D.

There are 50 numbers with an average of 83. Two numbers whose sum is 118 are removed. What is the average of the remaining numbers?

Four numbers have an average of 30. One of the numbers is replaced by 50, and the average becomes 40. What was the replaced number originally?

There are 72 students in Grade 5. Together they paid 52.5□ yuan as a recess snack fee. The boxed hundredths digit is unreadable. Every student paid the same amount, in whole cents (100 cents = 1 yuan). Calculate how much each student paid.

The average height of A and B is 1.68 m. The average height of B and C is 1.73 m. The average height of C and A is 1.60 m. What is the average height of A, B, and C?

A shop mixes 2 kg of crisp candy, 3 kg of fruit candy, and 5 kg of milk candy to make an assorted candy mix. Crisp candy costs 4.40 yuan per kilogram, fruit candy costs 4.20 yuan per kilogram, and the assorted mix costs 5.74 yuan per kilogram. Assume mixing loses no candy and adds no extra cost: the total cost of the mixture equals the combined cost of its ingredients. What is the price of the milk candy per kilogram?

At the weekend, Xiaoyang's family of five went mountain climbing. They walked 15 km, taking turns carrying two travel bags. Both bags were carried for the entire journey, with each carrier carrying one bag at a time. On average, how many kilometres did each person carry a travel bag?

Xiaoming's average on his previous mathematics tests was 84. Scoring 100 on the new test makes his overall average exactly 86. Which numbered test is this?

A factory's table of the number of machines produced during one week was damaged. Calculate the production on Wednesday and Thursday.

Xiaoming took six tests. The average of Tests 3 and 4 was 2 points higher than the average of the first two tests, and 2 points lower than the average of the last two tests. If the average of the last three tests was 3 points higher than the average of the first three tests, by how many points did Test 4 exceed Test 3?

Cups A, B, and C each contain some water. The amount in Cup B equals the average of the amounts in Cups A and C. If 15 mL of water is then added to Cup C without spilling any water, while A and B stay unchanged, the amount in Cup A equals the average of the amounts in Cups B and C. Which contains more water, Cup A or Cup B, and by how many millilitres?

During winter vacation, Xiaoming read Journey to the West. He read 83 pages on Day 1, 74 pages on Day 2, 71 pages on Day 3, and 64 pages on Day 4. The number of pages he read on Day 5 was 3.2 pages more than his average number of pages per day over all five days. How many pages did he read on Day 5?

The average weight of A, B, and C is 63 kg. The average weight of A and B is 3 kg greater than C's weight. A is 2 kg heavier than C. Find B's weight.

Six students had an average score of 92.5 on a mathematics examination. Their scores were distinct integers. The highest score was 99 and the lowest score was 76. When the scores are arranged from highest to lowest, what is the minimum possible score of the third-highest student?