设小明家现在总支出为A,需增加x%,根据题意,现在饮食支出为0.55A,所以
0.40≤[0.55A*(1+10%)]/[A*(1+x%)]≤0.49
即0.40≤[0.55(1+10%)]/(1+x%)≤0.49
解得23.47%≤x%≤51.25%
设小明家现在总支出为A,需增加x%,根据题意,现在饮食支出为0.55A,所以
0.40≤[0.55A*(1+10%)]/[A*(1+x%)]≤0.49
即0.40≤[0.55(1+10%)]/(1+x%)≤0.49
解得23.47%≤x%≤51.25%