# Tutor profile: Kevin T.

## Questions

### Subject: Medicine

A patient comes in with sudden onset weakness of the right upper extremity. A CT scan performed would likely reveal a stroke in the distribution of which cerebral artery? a.) Left middle cerebral artery b.) Right middle cerebral artery c.) Left anterior cerebral artery d.) Right anterior cerebral artery

Weakness indicates a stroke in the motor region of the brain. Motor input to the right side of the body is supplied by the left primary motor cortex. This immediately rules out b and d as the answers. Remember that the middle cerebral artery supplies the lateral area of the brain, while the anterior cerebral artery courses through the midsagittal area. Based on the homunculus, the upper extremity region is on the lateral surface. Hence the answer would be the left middle cerebral artery (A).

### Subject: Physics

A car traveling at 75 mph crashes into a stationary truck with a mass of 2000kgs. Afterwards, they move together at a speed of 15 mph. Assuming a frictionless system, what is the mass of the car?

This is a simple momentum question. Remember that the formula for momentum is: momentum = mass * velocity, or p = mv. Let m be that mass of the car Since we know that momentum should be conserved: momentum of car = momentum of car and truck m * 75 = (m + 2000) * 15 75m = 15m + 30000 60m = 30000 m = 500 The mass of the car is 500 kg

### Subject: Algebra

Alex is 8 years older than Sam. In 5 years, Alex will be twice as old as Sam. How old is Sam at present?

Let us assign the following variables: Alex's present age = x Sam's present age = y From the first statement, we get: x = y + 8 From the second statement, we get: x + 5 = 2 (y + 5) We can use the first equation to substitute for the second equation: (y + 8) + 5 = 2 (y + 5) y + 13 = 2y + 10 13 - 10 = 2y - y 3 = y We get the answer that Sam's present age is 3 years old. Double-checking the answer, we fill in the information x = 3 + 8 x = 11 11 + 5 = 2 (3 + 5) 16 = 2(8) 16 = 16 So we are sure that the answer is correct. Sam's present age is 3 years old.