a weight lifter uses both 2 kg blocks as well as 5 kg blocks to set up his bar. he has a total of 30 blocks if the total weight of the bar is observed to be 120 kg then calculate the number of 5 kg blocks and 2 kg blocks

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