GMAT: Math 49  Problem solving  GMAT  Khan Academy  Summary and Q&A
TL;DR
This video discusses solving GMAT math problems on topics such as coordinate geometry, reverse digits of a number, circle tangents, and parallel resistances, as well as probability calculations.
Questions & Answers
Q: How do you find the equation of a line in a coordinate system?
To find the equation of a line, you need to determine the slope using the change in y over the change in x, and the yintercept using a point on the line. The equation is typically written in the form y = mx + b, where m is the slope and b is the yintercept.
Q: How do you find the radius of a circle tangent to both axes?
Drawing a line from the center of the circle to the xaxis creates a right triangle. The distance from the center to the xaxis is equal to the radius. Using the Pythagorean theorem, you can find the radius in terms of the distance from the origin to the center of the circle.
Q: What is the formula for calculating combined resistance in parallel resistances?
The formula for calculating combined resistance in parallel resistances is 1/r = 1/x + 1/y, where r is the combined resistance and x and y are the individual resistances.
Q: How do you calculate the probability of a specific event occurring?
To calculate the probability of a specific event occurring, you multiply the probabilities of each independent event together. If there are events that should not occur, you subtract the probability of those events from 1 to find the probability of the desired event.
Summary & Key Takeaways

The video begins with a discussion of how to find the equation of a line in a coordinate system using slope and the yintercept.

It then moves on to solving a problem involving reversing the digits of a twodigit number and finding the difference between the original and reversed numbers.

The next problem involves finding the radius of a circle tangent to both axes, using the Pythagorean theorem and the distance from the origin to the center of the circle.

The video then covers the concept of parallel resistances in an electric circuit and how to calculate the combined resistance.

Finally, it concludes by solving a probability problem involving three individuals attempting to solve a problem, and finding the probability that two individuals solve it while the third does not.