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Practical problems in grade four of primary school The two cars left from the two places at the same time and met them two hours later. At this time, they were 20 kilometers away from the midpoint of the two places. It is known that car B travels 60 kilometers per hour and car a how many kilometers per hour
1. [(60 * 2-20) * 2-60 * 2] / 2 = 40 (km / h)
2. [(60 * 2 + 20) * 2-60 * 2] / 2 = 70 (km / h)
Twenty problems in the fourth grade
For example: 875 minus the product of 25 and 13, how many times the difference is 10?
First, find the difference: 875-25 * 13 = 550
How many times of 10: 550 / 10 = 55
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