A music store gives every 20th costumer a 5$ gift card. Every 50th customer gets a 10$ gift card. Which customer will be the first to receive both types of gift cards?

100th customer is the first desired customer who received both the gift cards.

Step-by-step explanation:

$5 gift card is received by every 20th Customer.

⇒ The customers who receive this $5 card are:

20th Customer, 40th Customer, 60th Customer, 80th Customer, 100th Customer, 120th Customer ... and so on

Also, $10 gift card is received by every 50th Customer.

⇒ The customers who receive this $10 gift are:

50th Customer, 100th Customer, 150th Customer, 200th Customer ...

Among all the customers the 100th customer is the first customer who receives $5 gift card as well as the $10 gift card.

Hence, 100th customer is the first desired customer who received both the gift cards.