Answer:
Step-by-step explanation:
Given the equation 
Step 1;
Expand the bracket at the right hand side of the equation to have:

Taking the reciprocal of both sides:

ANSWER: 2484
(Alternative forms): 2.484 × 10³
Answer:

Step-by-step explanation:
Given


Required
How fast is the ball seem to be moving?
This question illustrates relative velocity;
Since the ball and the train moves in the same direction, the required velocity relative to the person standing behind is:

i.e. we add both velocities


Two equivalent ratios for 30 to 6 can be 15 to 3 or 45 to 9