1.4.5×42= 189 km, 189 km is the express train.

2. (189-9) × 2 =180× 2 = 360 km, because 189 km just exceeds the midpoint of 9 km, so we have to subtract 9, which is only calculated.

The distance is half, so you have to multiply it by 2.

Two.

1.89.5+1.5 = 9 1, 91is the average of English and mathematics.

Points, 9 1×3=273 points, because there are 3 subjects, and×3 is the total score.

2.273-89.5×2=94, the total score minus English, and the numerical score is the English score.

Three.

There are still four days of water left. If water is calculated according to 16 days, no one has 16/40=0.4. The remaining 10*0.4=4, leaving just four days of water. So water just meets everyone's needs.

Four.

50 divided by 2=25, Mao Mao: 25+7=32, Dongdong: 25-7= 18, because under the same conditions, Mao Mao has 7 more and Dongdong has 7 less, so Mao Mao has +7 and Dongdong has -7.

Five.

For every x girls, there are x*7/6 boys.

(x+6)+x*7/6=(x+6)*4 1/20

x=54

So there are 54 girls.

Six.

3+5 = 8,5/8-1/ 2 =1/8,60 divided by 1/8=480 km, because a * * * accounts for 5/8 of B's garage, which is 60 km beyond the midpoint,1/.

Seven.

3/2= 1.5, 1.5×5=7.5, 7.5-3=4.5, because a * * *, there were 5 copies, 2 copies were made, and it took 3 hours, 1 used1.

5 copies is 7.5 hours-3 hours of use =4.5 hours.

Eight.

Solution: Suppose a * * * bought X colored balls.

2/5x+ 1/8x=3/5x- 15

x=200

Because 2/5x+ 1/8x is the number of the last red ball, and 3/5x- 15 is the number of other balls. The two are equal, and the above equation is obtained.

Nine.

Solution: Let the original price of this car be X yuan.

( 1+7%)x-0.95x=7200

x=60000

Very easy to understand. You don't need to explain.

Tongtenuto

Solution: Let this basket of apples weigh x kilograms.

1/5x+6= 1/2x

X=20 kilograms. (It's also easy to understand)

Eleven.

Express 1 hour 75 kilometers, and then 2 hours 150 kilometers. If it is 3km away from the midpoint, then150-3 =147km. Because 147 km is half the journey. So the total distance is 147×2=294 km. 294- 150 = 144km is the 2-hour journey of the local train, so the average hourly journey of the local train is 144/2 = 72km.

Twelve.

Solution: If the truck speed is X, the bus speed is 7/6x.

7/6x 4-x 4 = 36

x=54

So the truck speed is 54 kilometers per hour and the bus speed is 63 kilometers per hour.