myra's stamp collection consisted of 120 stamps in october. By the following march, her collection had grown to 138 stamps. By how much did her collection increase between october and march

18 stamp increase

15 % increase

Step-by-step explanation:

To find the increase in number, we take the number of stamps in march and subtract the stamps in october

128-120 = 18

To find the percent increase, we take the number of stamps that we gained over the original amount of stamps * 100%

percent increase = 18/120 * 100%

.15 * 100%

15% increase