48 km downstream, 5 hours upstream 16 km.
32 kilometers downstream and 24 kilometers upstream, it takes 5 hours.
Compared with the first time,
Water shortage: 48-32 =16km.
More current: 24- 16 = 8km.
So the downstream 16 km is the same as the upstream 8 km.
The downstream speed is 16÷8= twice the upstream speed.
It takes 48 kilometers to get along with water, and 48÷2=24 kilometers against the current.
The upstream speed is (24+16) ÷ 5 = 8km/h.
Downward speed is 8× 2 =16 km/h.
Still water speed: (8+ 16) ÷ 2 = 12km.
2.
The total number of students is a multiple of 5, and the unit of the total number is 5.
A multiple of three of the total number of boys,
The quotient of the total number of students divided by 5, odd number.
1×3=3
3×3=9, excluding
5×3=5, 5 repetitions, excluding.
7×3=2 1
9×3=27, excluding
The number of boys is a multiple of 3, so the sum of all the numbers is a multiple of 3.
Then try it separately
There are 3 boys, and there is no data that meets the requirements.
The number of boys is 1,
Boys: 26 1
Total: 26 1÷3×5=435
Meet the meaning of the question
So there are 435 people in this school.
3.
The sum of the numbers written by six people is: (87+92+98+99+104+10) ÷ 5 =118.
I don't understand what your topic means.
If you ask six children what is the closest sum of the numbers on the cards, it is 1 10.
4.
The remaining 52 cards, half red and half black, have 26 cards each.
The number of black in A is the same as the number of red in B..
Then the red in A and the black in B are the same.
Just look at a,
Black+Red =26 sheets
The red in A and the red in B add up to 26.
So the black in A is always equal to the red in B.
So the number of black cards in group A and red cards in group B will be exactly the same 1000 times.
5.
1= 1/2+ 1/2
= 1/2+ 1/3+ 1/6
The sum of the reciprocal of 2, 3 and 6 is equal to 1.