Wendy was asked to write an equation and solve this problem.

Dylan bought a box of markers. He used 14 markers and had 18 that he didn’t use. How many markers were in the box?

Wendy’s work is shown below.

Steps
Wendy’s Work
Step 1
m minus 14 = 18
Step 2
m minus 14 minus 14 = 18 minus 14
Step 3
m = 4

In which step, if any, did Wendy first make a mistake in her work?
step 1
step 2
step 3
no mistake

For every corresponding pair of cross sections, the area of the cross section of a sphere with radius r is equal to the area of the cross section of a cylinder with radius and height 2r minus the volume of two cones, each with a radius and height of r. a cross section of the sphere is and a cross section of the cylinder minus the cones, taken parallel to the base of cylinder, is the volume of the cylinder with radius r and height 2r is and the volume of each cone with radius r and height r is 1/3 pie r^3. so the volume of the cylinder minus the two cones is therefore, the volume of the cylinder is 4/3pie r^3 by cavalieri's principle. (fill in options are: r/2- r- 2r- an annulus- a circle -1/3pier^3- 2/3pier^3- 4/3pier^3- 5/3pier^3- 2pier^3- 4pier^3)