An island is 1.8 mi1.8 mi due north of its closest point on a straight shoreline. A visitor staying at a cabin on the shore that is 4.8 mi4.8 mi from that point. The visitor is planning to go from the cabin to the island. Suppose that the visitor runs at a rate of 6 mph6 mph and swims at a rate of 1 mph1 mph. How far should the visitor run before swimming to minimize the time it takes to reach the island

answer:

it is general formula that is used to write value to its excet position

a11 a12 a13

a21 a22 a23

it is the example of order 2 by 3 matrix in this

a11 means value occur in 1 st row 1st column

a12 means value occurs in 1st row 2nd column

a13 means value occur in 1st row and 3rd column

a21 means value occurs in 2nd row and 1st column

a22 means value occurs in 2nd row and in 2nd column

a23 means value occurs in 2nd row and in 3rd column

6mm^3 or .6cm^3

      216

      /   \

  36     6

  /   \     /

6     6   6

factor trees are nice.