Same signs: the product is positive. Different signs: the product is negative. (−6) × (−4) = 24, but (−6) × 4 = −24. Multiply the sizes first, then pick the sign.
Worked example
6 × (−4) = ?
Answer:−24
Different signs, so the product is negative. Multiply the sizes: 6 × 4 = 24. Answer: −24.
For grown-ups: Multiply/divide integers and rationals; sign rules. Below: three problems to try with the worked answers, and a free printable sheet. Children can practise the same skill as a game, with no sign-up and no ads.
CCSS 7.NS.A.2
What this practises, for teachers
Practices multiply/divide integers and rationals; sign rules (7.NS.A.2). A printable sheet with its answer key, worked answers on the page, no accounts.