Question

The mean of 20 numbers is 20. If 2 is added to each of the first ten numbers find the mean of the new set of 20 numbers

Answer 1

x1+x2+x3+x4+x5+x6+x7+x8+x9+x10+x11+x12+x13+x14+x15+x16+x17+x18+x19+x20/20=20
x1+x2+x3+x4+x5+x6+x7+x8+x9+x10+x11+x12+x13+x14+x15+x16+x17+x18+x19+x20=20*20
x1+x2+x3+x4+x5+x6+x7+x8+x9+x10+x11+x12+x13+x14+x15+x16+x17+x18+x19+x20=400 Let it be equation 1
x1+2+x2+2+x3+2+x4+2+x5+2+x6+2+x7+2+x8+2+x9+2+x10+2+
x11+x12+x13+x14+x15+x16+x17+x18+x19+x20/20
x1+x2+x3+x4+x5+x6+x7+x8+x9+x10+x11+x12+x13+x14+x15+x16+x17+x18+x19+x20+20/20 Let it be equation 2

put value from equation 1 in equation 2
400+20/20=420/20=21

Answer 2

hey friend!!!?

your answer is "21"

Explanation=>
_________

=> The mean of 20 no. is 20

hence sum of 20 no. will be = 20×20 = 400

if 2 is added to first 10 no. to total addition of 10×2 = 20

so after adding 20 to 400

total sum will be = 20+400=420

so avarege will be = 420/20 = 21



I think my answer is capable to clear your confusion...