Clock is broken. Reveal answer.

Yesterday I asked a puzzle about broken clock.

Today I am giving the answer and How did I solve it.

My first and clear approach was identified a total sum of 1 to 10 which is 55. But if we need to 4 pieces of 15 means total 60.

And sum of 11 and 12 is 23 which is not so helpful. But cleverly if you look we only need to add 5 more to 55. And sum of each digits of 11 and 12 is 5. But cutting them in half make available to sum individually.

Bingo. Viola. Ta da.

Thank you for your patience.