There are 42 students in class 1 and 38 students in class 2 of grade 6 in a school. The average score of all the students in the two classes in the final mathematics examination is 87. The average score of class 2 is 2 points higher than that of class 1. What is the average score of class 2?

There are 42 students in class 1 and 38 students in class 2 of grade 6 in a school. The average score of all the students in the two classes in the final mathematics examination is 87. The average score of class 2 is 2 points higher than that of class 1. What is the average score of class 2?

Total score of two classes: 87.45 * (42 + 38) = 6996
If the average score of class 1 is the same as that of class 2, each class will have 2 more points, and the total score will be more: 2 * 42 = 84 points
The total score is 6996 + 84 = 7080
At this time, the average score of the two classes is the average score of class 2: 7080 / (42 + 38) = 88.5

The topic is: the heart beats 54 times in 45 seconds, Xiao Hong says 72 times in one minute, is she right?
It is calculated by the method of solution proportion

1 minute = 60 seconds. 45 accounts for 75% of 60, so 54 divided by 72 is equal to 75%. The answer is right. Or 54 / 45 = 1.2, the heart beats 1.2 times in 1 second, 1 minute = 60 seconds, 60 * 1.2 = 72, so it is right

Mr. Liu went to the bookstore to buy books. Because of the large quantity of books, the shopkeeper gave a 20% discount. Therefore, Mr. Liu could buy five more books with 120 yuan. What was the original price of this book?

120 × 20% / 5% / 80% = 24% / 5% / 80%, = 4.8% / 80%, = 6 yuan. A: the original price of this book is 6 yuan