Jing tried to shade only prime numbers on the hundred chart.

Question

Jing tried to shade only prime numbers on the hundred chart.
However, Jing made a mistake.
hundred chart with 71, 73, and 75 shaded
$$91$$
$$81$$
$$71$$
$$61$$
$$51$$
$$41$$
$$31$$
$$21$$
$$11$$
$$1$$
$$92$$
$$82$$
$$72$$
$$62$$
$$52$$
$$42$$
$$32$$
$$22$$
$$12$$
$$2$$
$$93$$
$$83$$
$$73$$
$$63$$
$$53$$
$$43$$
$$33$$
$$23$$
$$13$$
$$3$$
$$94$$
$$84$$
$$74$$
$$64$$
$$54$$
$$44$$
$$34$$
$$24$$
$$14$$
$$4$$
$$95$$
$$85$$
$$75$$
$$65$$
$$55$$
$$45$$
$$35$$
$$25$$
$$15$$
$$5$$
$$96$$
$$86$$
$$76$$
$$66$$
$$56$$
$$46$$
$$36$$
$$26$$
$$16$$
$$6$$
$$97$$
$$87$$
$$77$$
$$67$$
$$57$$
$$47$$
$$37$$
$$27$$
$$17$$
$$7$$
$$98$$
$$88$$
$$78$$
$$68$$
$$58$$
$$48$$
$$38$$
$$28$$
$$18$$
$$8$$
$$99$$
$$89$$
$$79$$
$$69$$
$$59$$
$$49$$
$$39$$
$$29$$
$$19$$
$$9$$
$$100$$
$$90$$
$$80$$
$$70$$
$$60$$
$$50$$
$$40$$
$$30$$
$$20$$
$$10$$
What mistake did Jing make?
Choose 1 answer:
Choose 1 answer:
(Choice A)   
$$71$$ is composite, not prime.
A
$$71$$ is composite, not prime.
(Choice B)   
$$73$$ is composite, not prime.
B
$$73$$ is composite, not prime.
(Choice C)   
$$75$$ is composite, not prime.
C
$$75$$ is composite, not prime.

GPT-4o mini · Answer

The mistake Jing made was shading the number $75$.

To clarify:

$71$ is a prime number. It has no divisors other than $1$ and $71$.
$73$ is also a prime number. It has no divisors other than $1$ and $73$.
$75$, on the other hand, is not a prime number because it can be divided by $1, 3, 5, 15, 25,$ and $75$.

Therefore, the correct choice is:

(Choice C)
\[75\] is composite, not prime.