A 7th grade student answered 81 questions correctly on a 90-question test. What percent of the questions did she answer correctly?
What percent were incorrect?​

(81/90) x 100= 90%
Therefore 90% were correct

100%-90% = 10%
Therefore 10% were incorrect

38+105= 143, 39+104=143, and you will find then adding the numbers on opposite sides, moving inwards yields the answer 138 every time. because of this, you’re going to multiply 138 times the number of pairs, which is 34. therefore, 34*138= 4692(i’m sorry if it’s the wrong numbers, but it’s the right concept)