Final answer:
Dina's birthday was on a Tuesday. This was calculated by finding the remainder (6) when 125 was divided by 7, and counting backwards 6 days from Sunday.
Step-by-step explanation:
To determine on what day of the week Dina's birthday fell, we can use a simple mathematical technique that involves dealing with the modulo operation. The modulo operation gives us the remainder after division. In this context, we're interested in the remainder when dividing the number of days since Dina's birthday by the number of days in a week, which is 7.
First, we calculate 125 modulo 7:
125 ÷ 7 = 17 remainder 6
This means that 125 days is equivalent to 17 weeks plus 6 days. Since today is Sunday and we want to find the day of the week for Dina's birthday which was 125 days ago, we move 6 days back in the week from Sunday.
If we go backward 6 days from Sunday, we will land on:
- Monday
- Sunday
- Saturday
- Friday
- Thursday
- Wednesday
- Tuesday
So, Dina's birthday was on a Tuesday.