Answer:
8,146 x 121
Step-by-step explanation:
This is a problem in which you need to measure your understading of "orders of magnitude."
If the estimated answer is 
that means that we are looking at a multiplication in the "order of" 
You need to look at the "orders of magnitude" of the things you're multiplying. In the first case, we have 
that would be "of the order of" 
times 
. So the whole multiplication would "of the order of" 
or near 
The correct answer, 8,146 x 121, is because it's "of the order of" times 
and the gives us the we need.
Answer:
13
Step-by-step explanation:
its 13 calculator
.1225,.12, 7/125 the other fraction equals .12
Speed, S = Distance (d) / Time (t) => S= d/t => t= d/S
Let the speed of boat in still water be x mph
Resulting speed upstream = x-4 mph for a distance of 30 miles
Resulting speed downstream = x-4 mph for a distance of 50 miles
Time taken in both distances is equal.
Therefore,
30/(x-4) = 50/(x+4) => 30(x+4) = 50(x-4) => 30x+120 = 50x-200 => 120+200 = (50-30)x => 20x = 320 => x=320/20 = 16 mph
The speed of boat in still water is 16 mph.
