If Hannah and Stella work together on a project, they will complete it in 8 days. If Stella were to work with Riordan on the same project, they will take a day longer. If Riordan and Abigail work together, they will take 150% more time than Hannah and Stella. If Hannah and Abigail were to work together, how many more days will they take to complete the project compared to Stella and Riordan working together?
Time taken by Hannah and Stella in percent = 100%
Time taken by Riordan and Abigail = 100% + 150% = 250%

Time taken by Hannah and Stella = 8 days ---- (1)
Time taken by Stella and Riordan = 9 days ---- (2)
Time taken by Riordan and Abigail = 250% x 8 = 20 days ---- (3)

(1) + (2) + (3)
Hannah + Stella + Stella + Riordan + Riordan + Abigail → 8 + 9 + 20 = 37 days
Hannah + 2 (Stella + Riordan) + Abigail → 37 days
Hannah + Abigail + 2 x 9 → 37 days
Hannah + Abigail → 37 - 18 = 19 days

More days to complete the project for Hannah and Abigail compared to Stella and Riordan
= 19 - 9
= 10

Answer(s): 10