Answer:
-3.4 × 2.5 = -8.5
Explanation:
Since these are short decimals, you can probably convert these into fractions if you'd like.
So -3.4 = -17/5
And 2.5 = 5/2.
So just multiply this like you would multiply two fractions, just multiply across the numerator, and denominator, and then just simplify; numerator × numerator / denominator × denominator.
So
The trick when multiplying by 5 is to divide the number in half, and multiply by 10.
-17/5 × 5/2 = -17 × 5 / 5 × 2 = -17/2 × 10 / 10 = -8.5 × 10/10 = -8.5 × 1 = -8.5
(The tens just cancel and make 1 so you are just left with this answer)
You can also try splitting the decimals up into factors:
-3.4 × 2.5 = (-3 - 0.4)(2 + 0.5) = -6 + -0.8 + -1.5 + 0.2 = -6 + -1 + -1.5 = -7 + -1.5 = -8.5.