A distribution is written in inclusive form as 10–19, 20–29, 30–39, 40–49. The true class limits (class boundaries) of the class 20–29 are ____.

**Modal class**: class with HIGHEST frequency.

**Mode formula**:
**Mode = $l+h\times (f$₁ − $f$₀) / $(2f$₁ − $f$₀ − $f$₂)**

Where:
- $l$ = lower limit of modal class
- $h$ = class width
- $f$₁ = frequency of modal class
- $f$₀ = frequency of class BEFORE modal class
- $f$₂ = frequency of class AFTER modal class

**Example**: Modal class 30–40 with $f$₁ = 12, $f$₀ = 5, $f$₂ = 8. $l=30,h=10$.
Mode = $30+10\times (12-5)/(24-5-8)=30+\frac{70}{11}$ ≈ 36.36.