The school newly purchased 42 sets of single desks and chairs. Each table is 55 yuan, and each chair is 45 yuan. How much do you need to buy these desks and chairs?
学校新购买了42套单人课桌椅．每张桌子55元，每把椅子45元，购买这些课桌椅一共需要多少钱？
<gadget id="calculator">55 + 45</gadget>
<output>100</output>

<gadget id="calculator">100 * 42</gadget>
<output>4_200</output>

<result>4_200</result>