For the first time, in 1912, psychologist William Stern used the formula "mental age to chronological age x 100" to show IQ. Let's say someone was 10 years old and thought like a 10-year-old, their IQ would be 100. But if, say, they were 13 years old instead of 10, their IQ would be 130. Check https://iqtestonline.io

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IQ Test - Free & Accurate Online IQ Test With Instant Results

A free and certified IQ test designed to test how smart you are within minutes. Take the test, get instant results, and discover your IQ score without registration.