body {
  margin: 0 20%;
  background-color: #f0f0f0;
}

h3 {
  text-align: center;
  border: 1px solid #aaaaaa;
  border-radius: 10px;
  padding: 20px;
  background-color: #dadada;
}

.nombre {
  text-align: right;
}

#conversion {
  margin: 0 auto;
}

table {
  border-collapse: collapse;
  border: 1px solid black;
}

th {
  background-color: #dadada;
}

td, th {
  border-top: 1px solid black;
  padding: 1em;
  text-align: center;
}

button {
  width: 100px;
  height: 30px;
  font-size: 20px;
}