Aplain left los angeles and flew north at an average speed of 480 km/h. a cargo plane left to hours later and flew in the opposite direction with an average speed of 210 km/h. how long does the cargo plane need to fly before the planes are 5100 km apart?

The classic two trains problem:

http://mathforum.org/dr.math/faq/faq.two.trains.html

Step-by-step explanation:

its the fourth option

< coa = 150 ( given)

as ba and bc are tangents

so oc and oa is perpendicular to cb and ab respectively because in circle normal passes through centre

so in quadrilateral oabc

< coa + < oab + < ocb + < abc = 360

150 +90+90 + < abc = 360

330 + < abc = 360

< abc = 360 -330 = 30

so < abc = 30

⭐dhruv⭐