Hey!
Hope this helps...
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Now to solve this question all we need is basic math...
We know the water level (<em>at 1:00 pm</em>) started at 13in and than 30mins later it rose by 5in (<em>going to 18in</em>). Now an hour has passed and the water level has rose by 10in (<em>making it 28in in total</em>).
So, using basic math we can see that every 30mins the water level rises every 5in, and the equivalent ratio (simplified) is MINS to INCHES, 6min : 1in
So...
The answer is: Every 6mins the water level rises by 1in (rounded to the most simplified form).
ELSE
The answer is: Every 30mins the water level rises by 5in