To find true class limit should know the class size;

Class size = 31 – 26 = 5

Mid value = 5/2 = 2.5

When class mark is 26;

Upper class limit = 26 + 2.5 = 28.5

Lower class limit = 26 – 2.5 = 23.5

When class mark is 31;

Upper class limit = 31 + 2.5 = 33.5

Lower class limit = 31 – 2.5 = 28.5

When class mark is 36;

Upper class limit = 36 + 2.5 = 38.5

Lower class limit = 36 – 2.5 = 33.5

When class mark is 41;

Upper class limit = 41 + 2.5 = 43.5

Lower class limit = 41 – 2.5 = 38.5

When class mark is 46;

Upper class limit = 46 + 2.5 = 48.5

Lower class limit = 46 – 2.5 = 43.5

When class mark is 51;

Upper class limit = 51 + 2.5 = 53.5

Lower class limit = 51 – 2.5 = 48.5

So, true class limits are;

23.5 - 28.5, 28.5 - 33.5, 33.5 - 38.5, 38.5 - 43.5, 43.5 - 48.5, 48.5 - 53.5