Video Transcript
Daniel wants to buy groceries. He wants to have at least 80
dollars cash with him. And he currently has 15
dollars. Write and solve an inequality that
would determine how much cash Daniel should withdraw from the bank.
Daniel wants at least 80 dollars
cash. To find out what kind of inequality
we should write, let’s think about this. Would it be okay if Daniel had more
than 80 dollars cash? Yes. Would it be okay if Daniel had
exactly 80 dollars cash? Yes. It would not be okay if he had less
than 80 dollars cash. And that means we need an
inequality symbol that represents more or equal. We need the money Daniel has to be
greater than or equal to 80 dollars. And the money Daniel has consists
of two pieces. The money he should withdraw and
the 15 dollars he already has. Together, these two values should
be greater than or equal to 80 dollars. We can let the variable 𝑥
represent the money that Daniel will withdraw. And so we’re saying that 𝑥 plus 15
must be greater than or equal to 80.
At this point, we have successfully
written an inequality to show the money that Daniel needs. But we need to continue by solving
this inequality. We want to solve for what values of
𝑥 would this statement be true. And we do that by subtracting 15
dollars from both sides of the inequality. 80 dollars minus 15 dollars equals
65 dollars. 𝑥 must be greater than or equal to
65. And our 𝑥 represents the money
that he should withdraw from the bank. Daniel must withdraw at least 65
dollars if he wants to have 80 dollars cash with him. And so an inequality that we’ve
written 𝑥 plus 15 is greater than or equal to 80 and solved for 𝑥 must then be
greater than or equal to 65.
