1. **Problem statement:** Berenika wants to buy 35 T-shirts, each costing 5.80. She estimated the cost by calculating $40 \times 6 = 240$. 2. **Explain Berenika's calculation:** Berenika used rounded numbers: she rounded 35 up to 40 and 5.80 up to 6. Multiplying these gives $40 \times 6 = 240$. 3. **Why actual cost is less than 240:** Since 35 is less than 40 and 5.80 is less than 6, the actual cost $35 \times 5.80$ will be less than $40 \times 6 = 240$. 4. **Calculate actual cost without discount:** $$35 \times 5.80 = 203$$ 5. **Special offer:** Buy 30 or more T-shirts and get 10% off the total cost. 6. **Calculate discount:** 10% of 203 is $$0.10 \times 203 = 20.3$$ 7. **Calculate final cost after discount:** $$203 - 20.3 = 182.7$$ **Final answer:** The actual cost of buying 35 T-shirts with the special offer is **182.7**.