May-total income is 1000, mrs.Lee-600
June-total income 1120 ( 400+720), mrs.lee-720
thanks and the OA is A. Here is my problem. I understand exactly what you did. I know you got 400 by subtracting 600 from 1000 in the month of may, and then you added the 400 to 720 to end up with the total of 1120. since the question clearly stated that "If the rest of the family's income was the same both months", meaning that i could have also subtracted 720 from 1000 since it doesn't matter which month i pick, right? if i use that approach, i'll end up with 72% as my answer, which is wrong. how come the question mentions that the rest of the money is the same for both month, yet you could still get it wrong if you really treated them as equal? why did you choose the rest of the money from may rather than from june?
Mrs. Lee's income is 600 and the rest of the family's is 400. If Mrs. Lee's income increases to 720 and the rest of the family's income stays at 400 then the total is 1120. If you subtrack 720 from 1000 you will be reducing the rest of the family's income to 280 which is not the same at the original 400 they were making.