Estimate products by rounding factors first, then multiplying. For example, 23 × 4 ≈ 20 × 4 = 80. Estimating helps check if exact answers make sense.
Estimate and then compute to verify. Compare estimates to exact answers.
Not rounding correctly; multiplying before rounding; thinking estimates must be exact.
Estimation and exact calculation are two different tools for two different purposes. Exact calculation gives you a precise answer when you need one. Estimation gives you a quick, close-enough answer that you can use to plan, check, or decide — without doing the full computation. For multiplication, estimating products means using your rounding skills to replace the actual numbers with friendlier ones, then multiplying those instead.
The process has two steps: round first, then multiply. For 23 × 4, round 23 down to 20 (the nearest ten), then multiply: 20 × 4 = 80. The exact answer is 92, but 80 is close enough to tell you you're in the right neighborhood. For 48 × 6, round 48 up to 50: 50 × 6 = 300. The exact answer is 288 — your estimate of 300 is off by only 4%. That's plenty accurate for checking whether your calculation makes sense.
You already know how to round from your work on rounding whole numbers. The key insight here is that rounding makes multiplication easier because you're replacing a messy number with a multiple of 10 or 100, and you already know those products cold. 50 × 6 uses the basic fact 5 × 6 = 30 and then you add a zero. Estimation is really just rounding plus the multiplication facts you've already memorized — nothing new, just applied in a new context.
The most important use of estimation is checking exact answers. After computing 23 × 4 with a written method, you might get 82 or 92 or 102 — estimation tells you the answer should be around 80, so 82 and 92 are plausible but 102 is suspicious and worth checking again. This is why estimation isn't an alternative to exact computation — it's a watchdog that catches errors before they go unnoticed. Always estimate before or after you compute, and use the estimate to decide whether your exact answer is reasonable.