Billy got $50 from his mom as his weekly allowance. He went to the candy store and bought $7 worth of candy. How much money does Billy have left?

Since Billy spent money, this will be a subtraction problem. It is stated that Billy originally had $58 which will be your first number. Since Billy spent $7 on candy, this will be your second number that is being subtracted from $58. The problem looks like: 58 - 7 ---- First, the ones column is looked at where 8 - 7 = 1. Next the second column is looked at where 5 - nothing = 5. Bringing both number down gives us an answer of: 58 - 7 ----- 51 Check: Add the answer (51) to the number being subtracted (in this case 7) to see if we get the first number (58). 51 + 7 = 58 58 = 58 correct!

A roller coaster is moving with a speed of 19.7 m/s. The total weight of the roller coaster is 640 kg. Determine the kinetic energy of the roller coaster.

For this problem, we use the law of conservation of mechanical energy where it states that: KE = (0.5) * mass * (velocity)^2 where mass is in (kg) and velocity is in (m/s) inits. Therefore based on the problem, we have: KE = (0.5) * (640 kg) * (19.7 m/s)^2 KE = 124,189 Joules or 124.189 Kilojoules

The sum of two number is 67. One of the numbers is 9 more than the other. What are the two numbers?

The problem is asking to find two numbers. Therefore, we let x be one of them. In this case, x will be the first number in which we will solve for in order to find the second. It is stated that the other number is 9 more than x, or (x + 9). The problem also states that the sum of the two numbers is 67. Therefore, we will have: x + (x + 9) = 67 Add/subtract like terms where x + x will equal 2x and 9 will be subtracted from 67 to equal 58. We should get: 2x = 58 Now divide by 2 and x will be equal to 29. This is your first number. Recall that the second number is equal to 9 more than the first number, or (x + 9). If x is equal to 29, then: (29 + 9) = 38. The answer for this problem is the first number is 29 and the second number is 38. Check: 29 + (29 + 9) = 29 + 38 = 67 Correct!