Answer:
Step-by-step explanation:
John's age = w
His brother's age = 2*w = 2w
His sister's age = 16 years
Total age of all siblings = 31
w + 16 + 2w = 31
w + 2w + 16 = 31
Combine like terms
3w + 16 = 31
Subtract 16 from both sides
3w = 31 - 16
3w = 15
w = 15/3
w = 5

His brother's age = 2w
= 2*5
= 10

Answer:
Find the prime factorization of 14
14 = 2 × 7
Find the prime factorization of 6
6 = 2 × 3
Multiply each factor the greater number of times it occurs in steps i) or ii) above to find the lcm:
LCM = 2 × 3 × 7
LCM = 42
Answer:
A = 16 13unit^2 + 9unit^2 = 5 √10 = 15.8 = 16
Step-by-step explanation:
For Pythagoras we square route
= x^2 = 13^13 + (one of the closer squares for x elimination)
x= 169 + 81 169 + 100 169 + 49 169+64 169 + 121
x = 250 or 269 or 218 or 233 or 290
x= 5√10 or 15.8 or √269 269 or √218 2.8 or √233 or 2.33 ( or √290 = ( √48+2) or 2.9
24.8 divided by 175 is 0.1417142857142857 or you can round it to 0.142
Answer:
The half-life of the radioactive substance is of 3.25 days.
Step-by-step explanation:
The amount of radioactive substance is proportional to the number of counts per minute:
This means that the amount is given by the following differential equation:

In which k is the decay rate.
The solution is:

In which Q(0) is the initial amount:
8000 counts per minute on a Geiger counter at a certain time
This means that 
500 counts per minute 13 days later.
This means that
. We use this to find k.







So

Determine the half-life of the radioactive substance.
This is t for which Q(t) = 0.5Q(0). So







The half-life of the radioactive substance is of 3.25 days.