Answer: 20 minutes.
Explanation:
Think of the water stream as being still (perhaps like a solid pavement), from the point of view of objects floating on the surface. (of course, from the POV of anyone standing on the banks, the water flows downstream). Think of the boat as a bike riding on the pavement. The boat just turned upstream and the hat fell into the water. In this POV, the hat lies on the surface and the boat/bike is riding away. For 20 minutes. Then (Katya realizes she lost the hat and turns back), the boat/bike needs exactly the same time, i.e., 20 minutes to come back to the hat, which rests at the same spot on the surface!
What makes the question initially confusing is the fact that the river flows with respect to the banks and one's mind is tempted to view the situation from there, which makes it much more complicated.
In physics this is referred to as choosing the suitable "frame of reference."
Answer:
4 kid tickets and 3 adult tickets
Step-by-step explanation:
4 x 4 = 16 + 9 x 2 = 43(?)
Answer:
If two expressions are equal to each other, and you add the same value to both sides of the equation, the equation will remain equal. When you solve an equation, you find the value of the variable that makes the equation true. In order to solve the equation, you isolate the variable.
Answer:
Number 7 is 48
I think number 5 is 49 I'm not for sure about this one.
Step-by-step explanation:
Number 7:
Since it's a 90 degree angle, you just add 19 + 23 which gives you 42. Subtract 42 from 90 and it gives you 48, the value of the variable.
Number 5:
Now I'm not for sure about this one because of the number 12 pointing to the connecting point. So, I'd rather not say how I did this one before I get you confused when you learn about this in the future.
Answer:
9
Step-by-step explanation:
7r+18=r²
r²-7r-18=0
factorizing
r²+2r-9r-18=0
r(r+2)-9(r+2=0
(r-9)(r+2)=0
r-9=0
r=9
check
(r²)=(9*9)=81
7r+18=7(9) + 8=81
