Answer:
The number of the 2 kg blocks is 10
The number of the 5 kg blocks is 20
Step-by-step explanation:
Let the number of the 2 kg blocks be x and the number of the 5 kg blocks be y.
The total number of blocks in terms of x and y is;
x + y
We are informed that he has a total of 30 blocks, implying that;
x + y = 30
The total weight of the bar in terms of x and y will be;
2x + 5y
We are also informed that the total weight of the bar is observed to be 120, implying that;
2x + 5y = 120
We therefore have two equations in two unknowns.;
x + y = 30
2x + 5y = 120
We can solve these equations simultaneously via elimination method;
multiply the first equation by 2;
2x + 2y = 60
2x + 5y = 120
Subtracting the first equation from the second one yields;
5y - 2y = 120 - 60
3y = 60
y = 20
But x + y = 30, implying that;
x = 30 - 20
x = 10
