The core math is mostly correct, but the speaker uses ‘profit’ and ‘margin’ loosely and slightly understates the result after a 10% discount.
Claim-by-claim breakdown
Accurate (98% confidence): If an item costs 100 and is sold for 120, the profit is 20 on cost, but the profit margin is about 16.7% of the selling price. A cost of 100 and selling price of 120 gives profit of 20. Margin = profit ÷ selling price = 20 ÷ 120 = 16.7%.
Accurate (97% confidence): If you give a 10% discount off a 120 selling price on a product that costs 100, your profit falls to 8. 120 less 10% equals 108. With cost 100, profit is 8.
Accurate (91% confidence): After that 10% discount, the profit margin is about 7.4% of the selling price, not 6%. Discounted price is 108; profit is 8. Margin on final sale price is 8 ÷ 108 = 7.4%. On the original 120 price, profit is 8 ÷ 120 = 6.7%.
Accurate (90% confidence): The speaker's advice to use the correct calculation is important because confusing markup with margin can lead to pricing mistakes. Markup is profit as a percentage of cost, while margin is profit as a percentage of selling price.