Question

the mean of three numbers is 10.The mean of other four numbers is 12 .find the mean of all numbers

Answer 1

The mean of three numbers =10
So , Sum of three numbers =3×10 = 30
The mean of four numbers = 12
So, Sum of four numbers = 4×12 =48
Sum of seven numbers =30+48 =78
Mean of seven numbers =78/7 =11.14 (approximately )

Answer 2

$the \: mean \: of \: three \: numbers = 10 \\ so \: sum \: of \: three \: numbers = \: 3 \times 10 = 30 \\ the \: mean \: of \: four \: numbers = 12 \\ so \: sum \: of \: four \: numbers = \: 4 \times 12 = 48 \\ sum \: of \: seven \: numbers = 30 + 48 = 78 \\ mean \: of \: seven \: numbers = 78 \div 7 = 11.14 \: (approximately).$