The first elementary school second grade olympiad math questions and answers book 2.
Mother bought some chocolates, gave them to her neighbor's little sister and took them home. Xiaoya ate half of it first, and then gave the rest to her brother. At this time, there is 1 chocolate. How many chocolates did mom buy? Answer and analysis:
"My brother ate the remaining half, and there was 1 chocolate." The remaining half is 1, so before my brother eats, there is 1×2=2 (block), that is, after Xiaoya eats half, there are 2 pieces left, and before Xiaoya eats, there are 2×2=4 (block).
Another mother "gave her neighbor's little sister 2 pieces and took them home", so a * * * has 4+2=6 (pieces).
Mom bought six chocolates.
Test questions and answers of the second volume of Olympic mathematics in the second grade of primary school
1. There is a path from Bear's house to Pig's house. Plant a tree every 45 meters, plus 53 trees at both ends. Now plant a tree every 60 meters. How many trees are left? Answer: This question includes the problem of planting trees and the quantitative relationship between the two groups. The distance from Little Bear's house to Little Pig's house is 45×(53- 1)=2340 (m). After the change of spacing distance, 2340÷60+ 1=40 plants were planted between the two places, so there were 53-40= 13 plants.
2. Five people plant 20 trees in two hours, and six people plant how many trees in three hours?
Answer: To allow six people to plant trees in three hours, first ask the number of trees planted by five people in 1 hour, and then calculate the number of trees planted by 1 individual in 1 hour. 20÷5÷2×6×3=2×6×3=36 (tree). So six people planted 36 trees in three hours.
There is a circle of trees planted around the square playground, and trees are planted on all four corners, and every two trees are 5 meters apart. A and B start from a corner at the same time and go in different directions. A is twice as fast as B. After turning a corner, B meets A on the fifth tree (the tree in the corner is regarded as the first tree). How many trees are planted around the playground?
Answer: Because A's speed is twice that of B, B walks on one side of the playground, A walks on both sides, B turns a corner and walks to the fifth tree, which actually takes four intervals, so A should walk eight intervals, and the tree encountered is the ninth tree after A turns a corner, so there are 9+4= 13 trees on this side. There are (13- 1)×4=48 trees around the playground.
Students in a school plant trees, and each person shares the task of two trees. If a person works alone, it takes 10 minutes to dig a hole, 20 minutes to pick up seedlings (each person can take up to four trees at a time), 20 minutes to transport water (each person can water four trees at a time), and 1 0 minutes to plant trees. Ask one. How many minutes does it take if two people cooperate to make overall arrangements?
Answer: A person needs10× 2+20+20+10× 2 = 80 minutes; Two people need 20 (one person digs two holes and one person takes saplings) +20 (one person digs two holes and one person plants two trees) +20 (one person plants two trees and one person carries water) =60 minutes.
5. Plant trees on both sides of a 50-meter-long highway, and plant one tree every 10 meter, with two ends. How many trees have been planted on this road?
Answer: To plant trees on both sides of a 50-meter-long expressway, we should first consider how many trees to plant on one side, and plant 1 tree at both ends every 10 meter. There are five trees in 50 meters, which means there are five trees in the middle, so we can plant six trees on one side and six trees on both sides, which is 6+6 = 65433.
6. There are three trees in a park, and their age consists of two different numbers of 1, 2, 3, 4, 5 and 6, and one tree is exactly half the age of the other two trees. Do you know how old these three trees are?
Answer: The essence of this question is to divide the six numbers 1, 2, 3, 4, 5, 6 into three groups, and the two numbers in each group form two digits, so that the sum of the two digits is equal to twice the third digit. By the way, it is an important skill to turn interesting problems in life into pure mathematical problems. Students should pay attention to strengthening this ability from an early age, so as to use mathematical knowledge to solve difficult problems in practical work in the future. By careful observation and bold attempt, we can get three numbers, 12, 34, 56, because 12+56=34×2, that is, the age of these three trees is 12, 34, 56. There are several different answers to this question. Please use your head and find another answer.
Test questions and answers of Olympiad Mathematics in the second volume of Grade 2 in the third elementary school.
1. Fill in "+"or "-"where appropriate to make the equation hold. 123456= 1
2. Xiaohong is too careless in doing the problem. Take subtraction as an addition problem and mistake 25 for 52, and the result is 130. What is the correct result?
Analysis:
The first question:
Analysis of 1: grouping six numbers, you will find that1+2+3+5 =1,4+6= 10, so that "-"is filled in front of 4 and 6, and "+"is filled in other places, and the equation.
Analysis 2:1+2+3+4+5+6 = 21-1= 2020 ÷ 2 = 10 minus10 is enough.
Answer: 1+2+3-4+5-6= 1.
The second question:
Analysis: according to the conditions, list the correct formula and the wrong formula.
Correct: (78)-25=53
Error: (78)+52= 130