Two Way Data Binding (Calculations)

I'm trying to divide my gain and lotSize variable using two-way data binding but I keep getting these two errors :

1. The left-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type - (gain error)
2. The right-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type (lotSize error)

I'm new to using these frameworks but I get the feeling its something really basic. Any help you guys could provide would be really appreciated.

import { Component } from '@angular/core';
import { NavController } from '@ionic/angular';

@Component({
  selector: 'app-home',
  templateUrl: 'home.page.html',
  styleUrls: ['home.page.scss'],
})
export class HomePage {

  splash = true;

  constructor(public navCtrl: NavController) {
    //Splash Animation Timer
    setTimeout(() => this.splash = false, 4500);
  }

  //Calculation Variables
  entryPoint : Number = 0;
  gain : Number = 0;
  loss : Number = 0 ;
  lotSize : Number = 0;
  buyOrSell : Number = 0;

  //Calculation function buying and selling
  calculate = () => {
      let  rewardPips = (this.gain / this.lotSize) ;
  }

}

This the Html :

<ion-item>
      <ion-label position="stacked"><b>Entry Point # :</b></ion-label>
      <ion-input type="number" id="entryPoint" placeholder="0.000" [(ngModel)] = "entryPoint" clearInput></ion-input>
    </ion-item>
    <ion-item>
      <ion-label position="stacked"><b>Desired Monetary Gain $ :</b></ion-label>
      <ion-input type="number" id="gain" placeholder="0.000" [(ngModel)] = "gain" clearInput></ion-input>
    </ion-item>
    <ion-item>
      <ion-label position="stacked"><b>Willing Monetary Loss $ :</b></ion-label>
      <ion-input type="number" id="loss" placeholder="0.000" [(ngModel)] = 'loss' clearInput></ion-input>
    </ion-item>
    <ion-item>
      <ion-label position="stacked"><b>Trading Lot Size # :</b></ion-label>
      <ion-input type="number" id="lotSize" placeholder="0.000" [(ngModel)] = 'lotSize' clearInput></ion-input>
    </ion-item>

    <!--Grid With Checkbow Options-->
    <ion-grid>
      <ion-radio-group [(ngModel)] = "buyOrSell">
        <ion-row>
          <ion-col>
            <ion-item >
              <ion-label><b>Buy</b></ion-label>
              <ion-radio slot="start" value = "1" color="secondary"></ion-radio>
            </ion-item>
          </ion-col>
          <ion-col>
            <ion-item  >
              <ion-label><b>Sell</b></ion-label>
              <ion-radio slot="start" value = "0" color="secondary"></ion-radio>
            </ion-item>
          </ion-col>
        </ion-row>
      </ion-radio-group>
    </ion-grid>
    <br>
    <ion-button (click)="calculate()" color ="secondary" class="ion-activatable ripple-parent Primary" expand="block" shape="round">
      <h2><b>Calculate</b></h2>
      <ion-ripple-effect type="unbounded"></ion-ripple-effect>
    </ion-button>

  </ion-card>
</ion-content>