Answer:
c) d is greater than or equal to 530
Step-by-step explanation:
Hope this helps!
Try this solution:
Answer: 6 & 4.5 (m-per-h)
Step-by-step explanation:
- The basic formula used in this task is S=V*t, where S - distance, V - speed, t - time.
- the downstream speed is: V+Vc, where V - the speed of the boat in still water, Vc - the speed of the current.
- the upstream speed is: V-Vc.
- according to the described above the distance for downstream is S1=(V+Vc)*t1, where t1=10; the distance for upstream is S2=(V-Vc)*t2, where t2=70.
- for whole travel down- and upstream: S=S1+S2.
- Using these it is possible to make up the system of the equations:

V - the speed of the boat in still water - 6 miles per hour, Vc - the speed of the current - 4.5 miles per hour. All the details for the system of the equations are in the attachment.
Think of how many there are. im not sure if you put these into ratios or not...
like for number 3 think of how many numbers 1-9 are multiples of three
1 2 3 4 5 6 7 8 9
and once you get that number you make it out of 9 because there were 9 numbers
Example
3:9 3/9
for questions one and two its out of 52 and if you don't know how many clubs and hearts are in a deck you can look it up and put it in a ratio with 52
Well, let's just solve all these darn operations!
<em>14 + 2 = 16
</em><em>14 - 2 = 12
</em><em>14 * 2 = 28
</em><em>14 / 2 = 7
</em>
<em />So, what do you think the answer is? =)