Answer: 3 miles per hour
<u>Step-by-step explanation:</u>
Use the formula "distance (d) = rate (r) x time (t)" to create a system of equations.
Let "r" represent the rate they are rowing
Let "c" represent the current
time rate distance <u>EQUATION</u>
Downstream: 4 hours r + c 40 miles 4(r + c) = 40
Upstream: 10 hours r - c 40 miles 10(r - c) = 40
Distribute, then eliminate r to solve for c:
Down: 4r + 4c = 40 → 5(4r + 4c = 40) → 20r + 20c = 200
Up: 10r - 10c = 40 → -2(10r - 10c = 40) → <u>-20r + 20c</u> =<u> -80</u>
40c = 120
<u> ÷40 </u> <u>÷40 </u>
c = 3
Every number will have only 3 digits. In the ones place, there are 5 choices. For every choice of digit made in the ones place, there are 8 possible choices for the hundreds place (you can choose from 1-9, omitting whatever is used in the ones place), and there are 8 possible choices for the tens place (you can choose from 0-9, omitting whatever has already been used elsewhere).
So there are

such numbers.
<u>LCM on 539 and 15 :</u>
539 x 15
= 8 085
Answer : 8 085
0.48- Use a calculator if you need it. Use your multiples if needed. Hava a good day!