1/2 b . 1/3 c . 1/4d . 1/5
Example A, B and C are three weightlifters. The weight of three A's is equivalent to the weight of four B's, and the weight of three B's is equivalent to the weight of two C's. A is lighter than c 10 kg. How many kilograms does A weigh?
60-70 AD
Xiao Li had a meeting for more than an hour. At the beginning of the meeting, he looked at his watch. At the end of the meeting, he found that the hour hand and the minute hand had just exchanged places. How many minutes did this meeting last about 1 hour? ( )
5 1
Example: A 280-meter-long train with a speed of 20 meters per second passes a 2800-meter-long bridge. How long does it take for the train to cross the bridge completely? ( )
A.48b.2 minutes 20 seconds C.2 minutes 28 seconds D.2 minutes 34 seconds.
Example An empty drum with a volume of 64 liters has two holes A and B. A distilled water flows in from the hole A and out from the hole B. If the flow rate through the hole A is 3 liters/hour, how many liters can the container be filled in 96 hours? ()
A.4/3 B.8/3 C.7/3 D.3/7
Using the substitution method analytically, the final answer is 1/4, and choose C.
According to the topic, 3 A =4 B, 3 B =2 C, so A: C =8/9, one more copy, because one copy is 10 Jin, so 10? 8=80 kg, choose C.
Because the minute hand walks 6 degrees per minute and the hour hand walks 0.5 degrees per minute, the hour hand and the minute hand walk 30+360=390 degrees per hour. According to the topic, the hour hand and the minute hand switch positions. The hour hand walks a small part and the minute hand walks more than once, but actually it is a * * * that walks twice, which is 720 degrees, so 720/390 = 65438+.
Analyzing the problem of crossing the bridge, the formula is: the time from starting to getting on the bridge to getting off the bridge completely = (bridge length+vehicle length)/vehicle speed; So (2800+280)/20= 154s=2 minutes and 34 seconds, choose D.
By analyzing the inflow from hole A and outflow from hole B, assuming that the flow rate is X and the actual water storage speed of the container is 3-X, then 64/(3-X)=96, and X=7/3 is obtained.