At an elevation of 1221.4 feet, Lake Mead will hold 28,945,000 acre-feet of water. Which number is the best estimate of this amount of water?

3×10 6

2×10 7

2×10 7

3×10 7

2×10 8

The pyraminx is a rubik's cube-type toy in the shape of a tetrahedron. the pyraminx shown below has edges 15\,\text{cm}15cm long and vertical height h=12.2\,\text{cm}h=12.2cm. the triangle drawn with dashed lines is a right triangle. what is the distance rr? round your answer to the nearest tenth.