Why do fractions need to have a common denominator before you add or subtract them?

Cass decided to sell game programs for the hockey game. the printing cost was over 20 cents per program with a selling price of 50 cents each. cass sold all but 50 of the programs, and made a profit of $65. how many programs were printed? letting p represent the number of programs printed, set up an equation that describes this situation. then solve your equation for p.

The radius of the circle is 4 cm and the measure of the central angle is 90° the area of the sector with a central angle measuring 90° and radius of length 4 cm is vt cm the triangle in the sector is 4 cm the area of the triangle is v/cm² the area of the segment of the circle is (471 - ) cm?

Ascientist has discovered an organism that produces five offspring exactly one hour after its own birth, and then goes on to live for one week without producing any additional offspring. each replicated organism also replicates at the same rate. at hour one, there is one organism. at hour two, there are five more organisms. how many total organisms are there at hour seven? 2,801 19,531 19,607 97.655