Concept:
For a binomial distribution,
\[
\text{Variance} = npq
\]
where
• \(n\) = number of trials
• \(p\) = probability of success
• \(q = 1-p\)
Step 1: Find the value of \(q\).
\[
q=1-p
\]
\[
q=1-0.4=0.6
\]
Step 2: Substitute into the variance formula.
\[
\text{Variance}=npq
\]
\[
=10 \times 0.4 \times 0.6
\]
\[
=2.4
\]
Thus the variance is
\[
\boxed{2.4}
\]