If 10% of the television picture tubes burn out before their guarantees has expired: (a) What is the probability that a merchant who has sold 100 such tubes will be forced to replace 20 of them?
(b) What is the probability that he will replace at least 5 and not more than 15 tubes?

Two trains leave a station on different tracks. the tracks make an angle of 130°, with the station as a vertex. the first train travels 100 km and makes its first stop at point a, while the second train travels 200 km and makes it first stop at point b. how far apart are the trains when both are at their first stop? round the answer to the nearest integer. a) 65 km b) 139 km c) 224 km d) 275 km