Concrete blocks of length 1425m were laid end to end along the four side of a rectangular lawn 28m long and 21m wide how many blocks were required to complete one layer

The perimeter is the total length of all four sides.
Perimeter = 2 × (Length + Width)
Perimeter = 2 × (28 m + 21 m)
Perimeter = 2 × (49 m)
Perimeter = 98 m

The block length is given as 14_25m. Assuming this means 14.25 meters.
Length of one block = 14.25 m

Number of blocks = Perimeter / Length of one block
Number of blocks = 98 m / 14.25 m
Number of blocks ≈ 6.877

Since you cannot use a fraction of a block, you would need to round up to ensure the entire perimeter is covered. However, the question asks "how many blocks were required to complete one layer", implying an exact number if possible. Let's re-evaluate the block length interpretation.

If 14_25m means 14 and 2/5 meters:
14 2/5 m = 14 + (2/5) m = 14 + 0.4 m = 14.4 m

Let's try with 14.4 m:
Number of blocks = 98 m / 14.4 m
Number of blocks ≈ 6.805

This still results in a non-integer number of blocks. This suggests that either the numbers are not meant to result in an exact integer, or the interpretation of 14_25m is different.

Let's consider if 14_25m could mean 14.25 meters, and perhaps the problem expects rounding up.
If we must use whole blocks, we would need 7 blocks.

Let's assume the question implies an exact fit, and there might be a common factor or a different interpretation of 14_25m.
If it was 14 and 1/4 m (14.25 m), then 98 / 14.25 = 6.877...
If it was 14 and 2/5 m (14.4 m), then 98 / 14.4 = 6.805...

Given the context of concrete blocks, it's highly likely that the numbers are intended to work out nicely. Let's consider if 14_25m could be a typo for something like 14.0m or 14.5m or 14m.
If block length was 14m: 98/14 = 7 blocks. This is a clean number.
If block length was 14.5m: 98/14.5 = 6.75...

Let's proceed with the most common interpretation of 14_25m as 14.25m, and acknowledge that in a real-world scenario, you'd round up. However, for a math problem, if it doesn't divide evenly, it's worth double-checking the input.

Let's assume the question implies that the blocks fit perfectly, and there might be a slight misinterpretation of the block length or a typo in the problem. If we assume the block length was 14 meters for an exact fit:

Number of blocks = 98 m / 14 m = 7 blocks.

If we strictly use 14.25m, then:
Number of blocks = 98 / 14.25 ≈ 6.88. Since you can't use a partial block, you would need 7 blocks to cover the entire perimeter.

Let's go with the interpretation that 14_25m means 14.25 meters, and since blocks cannot be cut for this type of problem unless specified, we round up.

Number of blocks = 98 m / 14.25 m
Number of blocks = 6.877...

Since you cannot have a fraction of a block, you would need to purchase 7 blocks to ensure the entire perimeter is covered.

7 blocks