有含盐率为20%的盐水300克，要把含盐率提高到25%，应再加入（ ）克盐．
A．20
B．25
C．30
D．35
300×20%=60（克），
设再加入x克盐后，含盐率为25%，根据题意可得：
=25%，60+x x+300
60+x=75+0.25x，
x-0.25x=75-60，
0.75x=15，
x=20，
答：再加入20克盐后，含盐率为25%．
故选：A．
| 用方框里适当的短语完成句子。 | |
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