Giselle works as a carpenter and as a blacksmith. she earns $20, per hour as a carpenter and $25, per hour as a blacksmith. last week, giselle worked both jobs for a total of 30 hours and earned a total of \$690$690dollar sign, $690. how long did giselle work as a carpenter last week, and how long did she work as a blacksmith?

solution:

→c= a b , that is product of a and b is possible only when when a is m × n matrix and b is n × p matrix.

that is, number of columns of a= number of rows of b.

so, size of matrix , c= a b is , if a = (m × n)matrix

b= (n × p)matrix

then a b = [ (m × n)matrix] ×[   (n × p)matrix ]

→→c= a b= [m × p ] matrix

→→size of product a b will be equal to = number of rows of a × number of columns of b