In class 1500 students 1200 present find absent percentage

20%

Explanation:

Total number of students = 1500

Number of students present = 1200

Number of students absent = Total number of students - number of students present

Number of students absent = 1500 - 1200 =300

%number of students absent = 300 / 1500 * 100 = 20%

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally