An element with mass 970 grams decays by 27.7% per minute. How much of the element is remaining after 13 minutes, to the nearest 10th of a gram?

1-27.7% = 1-0.277 = 0.723
970*0.723^13 = 14.3 grams

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)