Answer:
600seconds
Step-by-step explanation:
If Ann can ice a cupcake in 30 seconds, then the total number of cupcakes iced by ann is t/30 cupcakes
Similarly, If Sarah can ice a cupcake in 40 seconds, then the total number of cupcakes iced by Sarah is t/40 cupcakes,
For them to ice 35cupcakes together, then;
t/30 + t/40 = 35
where t is the times taken by both of them to ice 35cupcakes
Find the LCM
40t+30t/1200 = 35
70t/1200 = 35
7t/120 = 35
t/120 = 5
t = 120 * 5
t = 600
This shows that it will take them both 600seconds to ice 35cupcakes
