A ship sets out to sail to a point 141 km due north. An unexpected storm blows the ship to a point 102 km due east of its starting point. (a) How far and (b) in what direction (as an angle from due east, where north of east is a positive angle) must it now sail to reach its original destination

Explanation:

The point of destination is 141 north and 102 km east . Vectorially it is represented by unit vector as follows .

D = 102 i + 141 j

magnitude of D = √ ( 102² + 141² )

= √ ( 10404 + 19881)

= √ 30285

= 174 km

To go back to original position , ship should move on the following vector

D = -102 i - 141 j

Tan Ф = 141 / 102 = 1.38

Ф = 54⁰ , direction will be south of west . From north  east , angle will be

180 + 54 = 234⁰

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form