Current location - Health Preservation Learning Network - Healthy weight loss - The school library is open, and 540 books are lent out in the middle grade, with the remaining 60% in the senior grade. At this time, the remaining books are just right.
The school library is open, and 540 books are lent out in the middle grade, with the remaining 60% in the senior grade. At this time, the remaining books are just right.
Set up x original books.
Total-middle school loan-high school loan = surplus.
X-540-(x-540)*60%=x*20%
(X-540)*( 1-60%)=x*20%
(X-540)*40%=X*20%
(X-540)*2=X
2X- 1080=X
X= 1080
Inspection: 1080-540 = 540
540*60%=324
540-324 = 2 16 is exactly equal to 20% of the total.