Each number from 1 to 60 is written on one of 60 index cards. the cards are arranged in rows with equal lengths and no cards are left over. The sum of of the numbers in each row is 305. How many rows are there?

Question

anonymous · Answer

plz help

anonymous · Answer

Total sum of 1~60 = 60*61/2=1830
# of Rows = r
1830=305*r
r=1830/305=6

There are 6 rows.

anonymous · Answer

erm.. wasn't the formula (first term+second term)*n/2=Sn?

anonymous · Answer

No it is (First Term + Last Term)*n/2=Sn

anonymous · Answer

Oh yes, but you didn't multiply n

anonymous · Answer

No, in this case, first term is 1 and last term is 60. So it is (1+60)*60/2 which is 61*60/2

anonymous · Answer

ahh ty