Uppdate value in datatable when using select statement

Hi

How do I put the amount back into the datatable with a new value when I have done a select statement?

DataRow[]  foundRow = dtPrev.Select("memno = '" + memno + "'" )
   if (foundRows.Length > 0)
            {
                for (int i = 0; i < foundRows.Length; i++)
                {

 amt = Convert.ToDecimal("10.95")+ Convert.ToDecimal(foundRows[i]["amount"].ToString());


// Here I need to put the amount back into the datatable


}
}

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