artistictails
Answered




Year .. Invention

----------------------------

1807.. Steamboat

1825 ..Photography

1837.. Telegraph

1846.. Sewing machine

1869.. Hydroelectric power

1876.. Telephone

1879.. Light bulb

1888 ..Rabies vaccine

1890 ..Diesel engine

1897 ..Airplane

--------------------------------



In Mr. Tarkiainen’s history class, each student chooses two of the topics listed in the chart above for their papers. How many different pairs can Juliana choose?


10

45

30

90

Verified Answer :

meerkat18

The answer is 90.

Since there are 10 topics listed in the chart above, and if you pair the first topic Steamboat you will get 9 pairs by pairing to all of the topics. And the same result you will get if you pair the last topic Airplane.

So if there are 10 topics and each will get 9 pairings , so the over all pairs you will get is 90.

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